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A1 noun #3,167 よく出る 9分で読める

不安定

fuantei 上位3,167

練習する例文メモとヒント 不安定 30秒で

解説 不安定 in your Level:

At the A1 level, you should learn '不安定' (fuantei) as a way to describe physical objects that are not steady. Think of a chair that wobbles or a ladder that feels like it might fall. You don't need to worry about complex grammar yet. Just remember that it means 'unstable'. You can use it in simple sentences like 'Kono isu wa fuantei desu' (This chair is unstable). It's a useful word because it helps you express when something feels unsafe or broken. At this stage, focus on the physical meaning. You might also hear it in very simple weather contexts, like when a teacher says the weather is 'unstable' so you should stay inside. The kanji might look difficult, but the first character '不' (not) is very common and will help you recognize many other words later on. Just think of 'fuantei' as the opposite of 'steady'.

At the A2 level, you can start using '不安定' (fuantei) to describe things beyond just physical objects. You might use it to talk about the weather ('fuantei na tenki') or your internet connection ('fuantei na setsuzoku'). You should also learn how to use it as a na-adjective. This means adding 'na' when it comes before a noun: 'fuantei-na isu' (an unstable chair). You will start to see this word in basic news headlines or weather reports. It's also a good time to learn the opposite word, 'antei' (stability). If you know 'antei', then 'fuantei' is just 'un-stability'. This makes it easier to remember! Try to use it when you are explaining why you can't do something, like 'The internet is unstable, so I can't watch the video.' This level is about connecting the word to daily problems and situations.

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At the B1 level, you should be comfortable using '不安定' (fuantei) in a wider range of contexts, including emotional and economic situations. You can describe someone's mood as 'fuantei' (emotional instability) or talk about 'fuantei na shigoto' (unstable work/freelancing). You should also learn common collocations like 'taiki no joutai ga fuantei' (unstable atmospheric conditions), which is a phrase used in almost every weather forecast. At this level, you can also start using adverbs to describe the degree of instability, such as 'totemo fuantei' (very unstable) or 'sukoshi fuantei' (a little unstable). You'll notice that 'fuantei' is a more formal and precise word than casual onomatopoeia like 'gura-gura'. Using 'fuantei' makes your Japanese sound more mature and descriptive, especially when discussing social issues or personal feelings in a serious way.

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At the B2 level, '不安定' (fuantei) becomes a key term for discussing abstract concepts like politics, economics, and science. You should be able to understand and use it in phrases like 'seiji-teki fuantei' (political instability) or 'keizai no fuantei' (economic instability). You will encounter this word frequently in newspapers (like the Asahi or Nikkei) and in academic texts. You should also understand its nuance in psychological contexts, such as 'joucho fuantei' (emotional instability/volatility). At this level, you should be able to compare 'fuantei' with similar words like 'ayaui' (precarious) or 'fukakujitsu' (uncertain) and choose the most appropriate one for the context. You should also be able to use the noun form in complex sentence structures, such as 'fuantei-sa o kokufu suru' (to overcome instability). This level requires you to use the word to analyze and describe complex systems and states.

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At the C1 level, you should have a nuanced understanding of '不安定' (fuantei) and its role in various specialized fields. In science, you might use it to describe 'fuantei na douitai' (unstable isotopes). In high-level political discourse, you might discuss 'shakai-teki fuantei yoin' (factors of social instability). You should be able to use the word with sophisticated grammar, such as 'fuantei-mei' (unstable-ness/instability) or in combination with other kanji compounds. You should also be sensitive to the register; 'fuantei' is often used in official reports to describe precarious situations without sounding overly emotional. You should be able to explain the causes and effects of instability using this word in long, coherent arguments. At this level, the word is not just a vocabulary item but a tool for precise conceptual analysis in professional and academic environments.

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At the C2 level, you should master '不安定' (fuantei) in all its metaphorical and technical applications. You can use it to discuss philosophical concepts of 'existential instability' or highly technical engineering failures. You should be able to understand its use in classical-style modern Japanese or very formal legal documents. You can distinguish between 'fuantei' and even more specific terms like 'hendou-sei' (volatility) or 'fukakutei-sei' (indeterminacy) in a way that shows a deep grasp of Japanese semantics. You should be able to use 'fuantei' in creative writing to evoke a sense of unease or transition. Your use of the word should be indistinguishable from a highly educated native speaker, utilizing it to describe the most subtle shifts in balance, whether they occur in a subatomic particle, a poem's meter, or a nation's soul.

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練習する例文メモとヒント

不安定 30秒で

不安定 (fuantei) means 'unstable' or 'instability', used for physical, emotional, and abstract contexts.
It acts as a na-adjective (不安定な) or a noun (不安定だ) in Japanese sentences.
Commonly heard in weather forecasts, news reports about the economy, and discussions about mental health.
The opposite of 'antei' (stability), it highlights a lack of balance or reliability in any system.

The Japanese word 不安定 (ふあんてい - fuantei) is a versatile noun and na-adjective that literally translates to 'instability' or 'unstable'. It is composed of two primary parts: 不 (fu), a prefix meaning 'not' or 'un-', and 安定 (antei), which means 'stability' or 'equilibrium'. When combined, they describe any state where balance is lacking, whether that balance is physical, emotional, economic, or atmospheric. In Japanese daily life, you will encounter this word in a variety of contexts, ranging from the mundane physical sensation of a wobbly chair to the complex fluctuations of global financial markets or the volatile nature of seasonal weather patterns in Japan.

Physical Instability: This refers to objects that are likely to fall over or lack a solid foundation. For example, a ladder placed on uneven ground is described as 'fuantei'. It emphasizes the risk of collapse or movement.
Emotional/Mental State: In psychology and daily conversation, it describes someone whose mood swings frequently or who is currently experiencing high levels of stress or anxiety. 'Seishinteki ni fuantei' (mentally unstable) is a common phrase used in clinical and social settings.
Meteorological Context: Weather forecasters in Japan frequently use 'fuantei' to describe atmospheric conditions that lead to sudden thunderstorms, especially during the transition between seasons or the rainy season (Tsuyu).

このはしごは足場が不安定だから、気をつけて登ってください。(Kono hashigo wa ashiba ga fuantei dakara, ki o tsukete nobotte kudasai.) - This ladder's footing is unstable, so please be careful when climbing.

Understanding 'fuantei' requires recognizing that it is not just a negative word; it is a descriptive one. In scientific contexts, it describes isotopes or chemical compounds that are reactive. In the tech world, an 'unstable' internet connection is 'fuantei na setsuzoku'. The word captures the essence of changeability and the lack of a fixed, reliable state. Because Japanese culture often values harmony (Wa) and stability, being 'fuantei' is generally something people seek to rectify or avoid, particularly in professional and social relationships.

午後は大気の状態が不安定になり、急な雨が降るでしょう。(Gogo wa taiki no joutai ga fuantei ni nari, kyuuna ame ga furu deshou.) - The atmospheric conditions will become unstable in the afternoon, and there will likely be sudden rain.

In summary, 'fuantei' is your go-to word for anything that isn't 'solid'. Whether you are talking about a wobbly table, a volatile stock market, or a friend who is going through a rough patch, 'fuantei' provides the necessary linguistic tool to describe that lack of equilibrium. It is a fundamental word for anyone looking to describe the complexities of the world around them in Japanese.

Using 不安定 correctly involves understanding its grammatical role as a na-adjective or a noun. Unlike English, where 'unstable' is primarily an adjective, Japanese allows 'fuantei' to function as a noun describing the state itself. When you want to modify another noun, you must add な (na). For example, 'an unstable job' becomes 'fuantei-na shigoto'. When it ends a sentence, you use the copula だ (da) or です (desu).

As a Na-Adjective: Structure: [Noun] + な + [Noun]. Example: 不安定な経済 (fuantei-na keizai) - Unstable economy. This is the most common way to use the word to describe specific objects or situations.
As a Noun with Particles: Structure: [Noun] + は + 不安定だ. Example: 彼の気持ちは不安定だ (Kare no kimochi wa fuantei da) - His feelings are unstable. Here, 'fuantei' acts as the predicate.

最近、インターネットの接続が非常に不安定です。(Saikin, intaanetto no setsuzoku ga hijou ni fuantei desu.) - Lately, the internet connection has been very unstable.

It is also important to note the adverbs often paired with 'fuantei'. Words like 極めて (kiwamete - extremely), 非常に (hijou ni - very), or 少し (sukoshi - a little) help quantify the level of instability. In formal reports, you might see 不安定極まりない (fuantei kiwamarinai), meaning 'nothing could be more unstable'.

その政権は、支持率の低下により不安定な状態にあります。(Sono seiken wa, shijiritsu no teika ni yori fuantei na joutai ni arimasu.) - That administration is in an unstable state due to the decline in approval ratings.

When discussing people, 'fuantei' can sound a bit clinical. If you are talking to a friend about their emotions, you might use 'fuantei' to show concern, but be aware that calling someone 'unstable' (fuantei na hito) can be perceived as a strong judgment about their character or mental health. Context is key to ensuring your use of the word remains respectful and accurate.

You will encounter 不安定 (fuantei) across a wide spectrum of Japanese media and daily life. It is not a word confined to textbooks; it is a living part of the language used by professionals and laypeople alike. Understanding the environments where this word thrives will help you grasp its nuances and frequency.

News and Media: The news is perhaps the most common place to hear 'fuantei'. News anchors use it to describe fluctuating stock prices (kabuka no fuantei), political turmoil in foreign countries (seiji no fuantei), or the precarious state of international relations.
Weather Forecasts (Tenki Yohou): Every morning, weather reports use the phrase 'taiki no joutai ga fuantei' (the atmospheric state is unstable). This is a standard warning for commuters to bring an umbrella, as it implies unpredictable rain or storms.
Workplace and Engineering: In technical fields, engineers use 'fuantei' to describe software bugs, flickering lights, or shaky scaffolding. If a system is 'fuantei', it needs immediate troubleshooting.

世界情勢が不安定なため、原油価格が高騰しています。(Sekai jousei ga fuantei na tame, genyu kakaku ga koutou shite imasu.) - Because the global situation is unstable, crude oil prices are skyrocketing.

In the medical and health industry, 'fuantei' is used to describe vital signs or mental states. A patient's pulse might be 'fuantei', or their recovery might be in an 'unstable' phase. This usage highlights the word's role in describing critical, non-steady states that require observation.

彼女は最近、情緒不安定で、よく泣いています。(Kanojo wa saikin, joucho fuantei de, yoku naite imasu.) - She has been emotionally unstable lately and cries often.

Finally, in the context of the gig economy or modern employment, 'fuantei na koyou' (unstable employment) is a major social topic in Japan. It refers to part-time, temporary, or contract work that lacks the security of the traditional lifetime employment system. This specific usage reflects modern Japanese social anxieties.

While 不安定 (fuantei) is relatively straightforward, learners often make a few common errors, particularly regarding its grammatical classification and its nuance compared to similar-sounding concepts like 'danger' or 'fear'.

Mistaking it for an I-Adjective: Learners sometimes try to say 'fuantei-i' or 'fuantei-kunai'. Remember, 'fuantei' is a na-adjective. The negative form is 'fuantei dewa nai' or 'fuantei ja nai', and the modifying form is 'fuantei-na'.
Confusing Unstable with Dangerous (Abunai): While something 'fuantei' can be 'abunai' (dangerous), they are not synonyms. 'Fuantei' describes the *state* of balance, while 'abunai' describes the *risk* of harm. A wobbly chair is 'fuantei', but sitting on it might be 'abunai'.
Overusing it for 'Shaky' (Gura-gura): For physical shaking, like a loose tooth or a table leg, Japanese speakers often prefer the onomatopoeia 'gura-gura'. 'Fuantei' is more abstract and formal. Using 'fuantei' for a loose tooth sounds overly technical and unnatural.

❌ 不安定い椅子 (Fuantei-i isu)
✅ 不安定な椅子 (Fuantei-na isu) - An unstable chair.

Another mistake is forgetting the 'fu' (negative) prefix. Some learners confuse 'antei' (stability) with 'fuantei' (instability) when speaking quickly. Always double-check that you've included the 'fu' if you mean things are shaky! Additionally, ensure you don't confuse it with 'fuan' (anxiety). While related, 'fuan' is the feeling of worry, whereas 'fuantei' is the state of being unstable.

❌ 彼は不安定だ (Kare wa fuantei da - He is unstable [mental state]) when you mean ❌ 彼は不安だ (Kare wa fuan da - He is anxious/worried).

Lastly, be careful with the particle usage. When saying 'unstable in [category]', use the particle 'ga'. For example, 'shijiritsu ga fuantei' (approval rating is unstable). Using 'no' or 'ni' incorrectly here is a common pitfall for English speakers trying to translate 'unstable in' literally.

To truly master 不安定 (fuantei), you should understand how it compares to other Japanese words that describe lack of stability or balance. Depending on whether the context is physical, emotional, or structural, a different word might be more appropriate.

ぐらぐら (Gura-gura): This is an onomatopoeic word (gitaigo) used for physical wobbling. While 'fuantei' is formal and abstract, 'gura-gura' is vivid and sensory. Use 'gura-gura' for a loose tooth or a table that shakes when you touch it.
危うい (Ayaui): Meaning 'precarious' or 'dangerous', this word implies that a situation is on the verge of disaster. 'Fuantei' means it's not steady; 'ayaui' means it's about to fail. Example: 'Ayaui tachiba' (a precarious position).
揺らぐ (Yuragu): A verb meaning 'to waver' or 'to shake'. This is often used for abstract things like 'faith' or 'determination'. While 'fuantei' describes the state, 'yuragu' describes the action of losing stability. 'Kesshin ga yuragu' (determination wavers).

比較：
1. 机がぐらぐらする (Physical wobble)
2. 雇用が不安定だ (Economic instability)

Other alternatives include 不規則 (fukisoku - irregular), which focuses on the lack of a pattern, and 不確実 (fukakujitsu - uncertain), which focuses on the lack of certainty. If you are describing a person's behavior that changes without reason, 気まぐれ (kimagure - moody/whimsical) might be a more natural fit than the clinical 'fuantei'.

将来が不透明で、経済も不安定だ。(Shourai ga futoumei de, keizai mo fuantei da.) - The future is opaque (unclear), and the economy is also unstable.

By learning these synonyms and their specific contexts, you can avoid the 'one-word-fits-all' trap and express yourself with the precision of a native speaker. 'Fuantei' is a powerful word, but knowing when to use 'gura-gura' or 'ayaui' will make your Japanese sound much more natural and expressive.

How Formal Is It?

豆知識

The character '安' (an) depicts a woman under a roof, symbolizing peace and stability. Adding '不' (not) at the beginning literally removes the woman from the roof, implying the loss of that peace.

発音ガイド

UK /ɸɯ.an.teː/

US /fu.an.teɪ/

Japanese does not have stress accent like English, but rather pitch accent. In 'fuantei', the pitch usually starts low on 'fu' and rises on 'antei'.

韻が合う語

Kantei (鑑定 - appraisal) Sentei (選定 - selection) Zentei (前提 - premise) Antei (安定 - stability) Gentei (限定 - limitation) Kentei (検定 - certification) Santei (算定 - calculation) Tantei (探偵 - detective)

よくある間違い

Pronouncing 'fu' like an English 'f' with teeth touching lips.
Shortening the long 'ei' sound at the end.
Failing to pronounce the 'n' clearly before the 't'.
Adding a stress accent on one of the syllables.
Confusing the pitch with 'fuan' (anxiety).

難易度

読解 3/5

The kanji are common but require intermediate knowledge. The first character '不' is easy, but '定' can be confused with others.

ライティング 4/5

Writing '不安定' requires remembering the stroke order for '安' and '定', which are standard but essential.

スピーキング 2/5

The pronunciation is straightforward with no difficult sounds for English speakers.

リスニング 2/5

The word is very distinct and frequently used in media, making it easy to pick out.

次に学ぶべきこと

前提知識

不 (fu - not) 安 (an - cheap/peace) 定 (tei - fix) 安定 (antei - stability) 天気 (tenki - weather)

次に学ぶ

不規則 (fukisoku - irregular) 不確実 (fukakujitsu - uncertain) 平衡 (heikou - equilibrium) 維持する (iji suru - to maintain) 崩壊 (houkai - collapse)

上級

地政学的リスク (chiseigaku-teki risuku - geopolitical risk) 揮発性 (kihatsu-sei - volatility) 脆弱性 (zeijaku-sei - vulnerability) 均衡の破綻 (kinkou no hatan - breakdown of equilibrium)

知っておくべき文法

Na-Adjective Modification

不安定な(na) + Noun

Adverbial form with 'ni'

不安定に(ni) + Verb (e.g., 不安定に揺れる)

State change with 'naru'

不安定に(ni) + なる (naru)

Reason with 'de'

不安定で(de) + Clause (Because it is unstable...)

Polite Negative

不安定ではありません (fuantei dewa arimasen)

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レベル別の例文

このいすは不安定です。

This chair is unstable.

Uses the basic 'Noun wa Adjective desu' pattern.

机が不安定ですね。

The desk is unstable, isn't it?

The particle 'ne' is added for agreement.

不安定なはしご。

An unstable ladder.

Shows 'fuantei' as a na-adjective modifying a noun.

足場が不安定だ。

The footing is unstable.

Common phrase for physical instability.

不安定だから気をつけて。

It's unstable, so be careful.

Uses 'kara' to mean 'because'.

その箱は不安定です。

That box is unstable.

Simple identification of state.

不安定な場所。

An unstable place.

Adjective + Noun structure.

カメラが不安定だ。

The camera is unstable.

Subject + Particle 'ga' + Adjective.

今日は天気が不安定です。

The weather is unstable today.

Contextual shift to weather.

ネットが不安定で困る。

The internet is unstable, and it's a problem.

Uses the '-te' form of 'fuantei' (which is 'fuantei de') to connect clauses.

不安定な天気ですね。

It's unstable weather, isn't it?

Na-adjective modifying 'tenki'.

接続が不安定になりました。

The connection became unstable.

Uses 'ni naru' to show a change in state.

不安定な仕事はしたくない。

I don't want to do unstable work.

Negative desire 'takunai'.

このテーブルは少し不安定だ。

This table is a little unstable.

Adverb 'sukoshi' modifies the adjective.

不安定な生活をしています。

I am living an unstable life.

Describes a lifestyle using 'fuantei-na'.

午後は天気が不安定になるでしょう。

The weather will likely become unstable in the afternoon.

Future/Probable 'deshou'.

大気の状態が不安定で、雷が鳴っています。

The atmospheric conditions are unstable, and thunder is rolling.

Formal weather forecasting terminology.

試験の前は気持ちが不安定になりやすい。

Before an exam, one's feelings tend to become unstable.

Uses 'yasui' (tends to/easy to).

彼は情緒不安定なところがある。

He has some emotional instability.

Compound 'joucho fuantei' (emotional instability).

不安定な収入では家は買えない。

You can't buy a house with an unstable income.

Potential negative 'kaenai'.

世界情勢は依然として不安定だ。

The world situation remains unstable.

Adverb 'izen to shite' (as ever/still).

パソコンの動作が不安定になった。

The computer's operation became unstable.

Technical usage of 'fuantei'.

不安定な雇用形態が社会問題になっている。

Unstable forms of employment are becoming a social problem.

Noun phrase 'koyou keitai' (employment form).

物価が不安定で、買い物が大変だ。

Prices are unstable, so shopping is difficult.

Uses '-de' for reason/cause.

株価が不安定な動きを見せている。

Stock prices are showing unstable movements.

Collocation 'fuantei na ugoki' (unstable movement).

政権の基盤が不安定になってきた。

The foundation of the administration has started to become unstable.

Auxiliary verb '-te kita' (has come to be).

中東の情勢は極めて不安定だ。

The situation in the Middle East is extremely unstable.

Adverb 'kiwamete' (extremely).

不安定な精神状態を克服する必要がある。

It is necessary to overcome an unstable mental state.

Verb 'kokufuku suru' (to overcome).

供給が不安定なため、納期が遅れます。

Because the supply is unstable, the delivery date will be delayed.

Formal reason 'tame'.

不安定な要素を排除しなければならない。

We must eliminate the unstable elements.

Must-do 'nakereba naranai'.

景気の回復はまだ不安定な段階にある。

The economic recovery is still in an unstable stage.

Noun 'dankai' (stage/phase).

不安定な気圧配置により、天気が急変した。

Due to an unstable pressure pattern, the weather changed suddenly.

Compound 'kiatsu haichi' (pressure distribution).

その同位体は極めて不安定で、すぐに崩壊する。

That isotope is extremely unstable and decays immediately.

Scientific context (isotopes and decay).

不安定な社会情勢が投資を抑制している。

The unstable social situation is suppressing investment.

Verb 'yokusei suru' (to suppress/restrain).

このアルゴリズムは、特定の条件下で不安定になる可能性がある。

This algorithm has the potential to become unstable under certain conditions.

Abstract technical possibility 'kanousei ga aru'.

不安定な足場での作業は、厳格な安全基準が求められる。

Work on unstable footing requires strict safety standards.

Passive 'motomerareru' (is required).

為替相場が不安定なため、輸出企業は苦戦している。

Because the exchange rates are unstable, exporting companies are struggling.

Compound 'kawase souba' (exchange market).

不安定な雇用は、少子化の要因の一つとされている。

Unstable employment is considered one of the factors of the declining birthrate.

Passive 'to sarete iru' (is said to be/considered).

彼の理論は、前提条件が不安定であるという批判を受けた。

His theory received criticism that its prerequisites were unstable.

Noun 'zentei jouken' (prerequisites/premises).

気候変動により、食料供給が不安定化している。

Food supply is becoming unstable due to climate change.

Verb 'fuantei-ka suru' (to become unstable/destabilize).

量子力学的な不安定性は、現代物理学の核心的な課題である。

Quantum mechanical instability is a core challenge of modern physics.

Noun 'fuantei-sei' (instability/unstable-ness).

地政学的な不安定さが、グローバルな供給網に深刻な打撃を与えた。

Geopolitical instability dealt a serious blow to global supply chains.

Compound 'chiseigaku-teki' (geopolitical).

不安定な均衡の上に成り立つ平和は、長くは続かない。

A peace built upon an unstable equilibrium will not last long.

Metaphorical 'fuantei na kinkou' (unstable equilibrium).

その新薬は、化学的に不安定なため、保存には細心の注意を要する。

Because the new drug is chemically unstable, its storage requires meticulous care.

Formal 'yousuru' (to require).

不安定な情緒を抱えながらも、彼女は舞台に立ち続けた。

Despite harboring unstable emotions, she continued to stand on the stage.

Concessive '-nagara mo' (while/despite).

マクロ経済の不安定要因を精査し、適切な対策を講じるべきだ。

We should scrutinize the macro-economic instability factors and take appropriate measures.

Formal 'koujiru' (to take measures).

不安定な地盤の上に巨大な建築物を建てるのは、技術的な挑戦である。

Building a massive structure on unstable ground is a technical challenge.

Noun 'jiban' (ground/foundation).

市場の不安定化を避けるため、中央銀行が介入した。

The central bank intervened to avoid market destabilization.

Nominalized 'fuantei-ka' (destabilization).

類義語

不確実危ういぐらつく不規則変動的

反対語

安定固定一定

よく使う組み合わせ

情緒不安定

大気が不安定

経済が不安定

不安定な雇用

不安定な足場

接続が不安定

不安定な政治

精神的に不安定

不安定な供給

不安定な均衡

よく使うフレーズ

不安定な天気

— Unpredictable or changeable weather conditions.

不安定な天気が続くので、傘を常備しましょう。

不安定な状態

— A state or condition that is not steady or reliable.

患者の容体は依然として不安定な状態です。

不安定な椅子

— A wobbly or shaky chair.

不安定な椅子に座って、転びそうになった。

不安定な基盤

— An unreliable or shaky foundation (physical or abstract).

この計画は不安定な基盤の上に成り立っている。

不安定な立場

— An insecure or precarious position (e.g., at work).

契約社員という不安定な立場で働いている。

不安定な気持ち

— Unsettled or fluctuating feelings.

将来のことを考えると、不安定な気持ちになる。

不安定な収入

— Income that is not regular or guaranteed.

フリーランスは不安定な収入が悩みだ。

不安定な時代

— An era of instability or rapid, unpredictable change.

私たちは今、不安定な時代を生きている。

不安定な波

— Irregular or unpredictable waves/cycles.

景気の不安定な波に翻弄される。

不安定な姿勢

— An unbalanced or shaky physical posture.

不安定な姿勢で重いものを持たないでください。

よく混同される語

不安定 vs 不安 (fuan)

Fuan means 'anxiety' or 'worry' (a feeling), while fuantei means 'instability' (a state).

不安定 vs 危ない (abunai)

Abunai means 'dangerous'. Something unstable (fuantei) might be dangerous, but they are not the same thing.

不安定 vs 不便 (fuben)

Fuben means 'inconvenient'. Some learners confuse the 'fu' prefix words.

慣用句と表現

"不安定な船出"

— A shaky start to a new venture or journey.

新会社の経営は不安定な船出となった。

Metaphorical

"綱渡りのような不安定さ"

— Instability comparable to walking a tightrope.

彼の生活は綱渡りのような不安定さだ。

Informal

"氷の上を歩くような不安定さ"

— Instability like walking on thin ice.

今の関係は氷の上を歩くような不安定さがある。

Literary

"根無し草のような不安定さ"

— Instability like a rootless weed (drifting).

彼は根無し草のような不安定な生活を送っている。

Literary

"砂上の楼閣"

— A castle on sand (something built on an unstable foundation).

その計画は砂上の楼閣で、非常に不安定だ。

Formal

"風前の灯火"

— A flame before the wind (extremely unstable/precarious).

その政権の命運は風前の灯火で、極めて不安定だ。

Formal

"危うきこと累卵のごとし"

— As precarious as a pile of eggs (extremely unstable).

国家の存亡は危うきこと累卵のごとく不安定だ。

Literary/Archaic

"不安定な天秤"

— An unbalanced scale (unfair or unstable comparison).

二つの価値観が不安定な天秤にかかっている。

Metaphorical

"五里霧中"

— Lost in a fog (unstable and unclear direction).

将来が五里霧中で、非常に不安定な気分だ。

Idiomatic

"薄氷を踏む"

— Treading on thin ice (highly unstable situation).

薄氷を踏むような不安定な交渉が続いた。

Formal

間違えやすい

不安定 vs 不規則 (fukisoku)

Both imply a lack of a steady state.

Fukisoku specifically means 'irregular' or 'no pattern' (like a heartbeat), while fuantei means 'unstable' or 'lacking balance'.

不規則な生活 (Irregular lifestyle) vs 不安定な生活 (Unstable life).

不安定 vs 流動的 (ryudouteki)

Both mean things are changing.

Ryudouteki means 'fluid' or 'subject to change' (like a plan), while fuantei implies a risk of falling or failing.

予定は流動的だ (The schedule is fluid) vs 予定は不安定だ (The schedule is unstable/unreliable).

不安定 vs 不確実 (fukakujitsu)

Both deal with things that aren't solid.

Fukakujitsu means 'uncertain' or 'not guaranteed', while fuantei means 'shaky' or 'volatile'.

不確実な未来 (Uncertain future) vs 不安定な未来 (Unstable/volatile future).

不安定 vs 危うい (ayaui)

Both describe precarious states.

Ayaui has a stronger sense of 'imminent danger' or 'about to be lost', whereas fuantei is a general state of being shaky.

危うい命 (A life in danger) vs 不安定な容体 (Unstable condition).

不安定 vs ふらふら (fura-fura)

Both describe shakiness.

Fura-fura is used for a person's physical dizziness or aimless wandering, while fuantei is more formal and general.

頭がふらふらする (My head is spinning) vs 精神的に不安定だ (Mentally unstable).

文型パターン

[Object] は不安定です。

この椅子は不安定です。

不安定な [Noun] ですね。

不安定な天気ですね。

[Noun] が不安定になりました。

接続が不安定になりました。

[Noun] が不安定なため、[Result]。

天気が不安定なため、中止します。

[Abstract Noun] の不安定さが目立つ。

経済の不安定さが目立つ。

不安定な [Noun] を克服する。

不安定な精神状態を克服する。

[Noun] が不安定化している。

情勢が不安定化している。

不安定な均衡の上に成り立つ。

不安定な均衡の上に成り立つ平和。

語族

名詞

不安定 (fuantei - instability)

不安定性 (fuanteisei - unstable-ness)

安定 (antei - stability)

不安定化 (fuanteika - destabilization)

動詞

不安定化する (fuanteika suru - to destabilize)

安定させる (antei saseru - to stabilize)

安定する (antei suru - to become stable)

形容詞

不安定な (fuantei-na - unstable)

安定した (antei-shita - stable/steady)

使い方

frequency

Very High. Used in daily conversation, news, and technical documents.

よくある間違い

Using 'fuantei' as an i-adjective (e.g., fuantei-i). → fuantei-na (na-adjective).
Fuantei is a na-adjective/noun. It does not follow the conjugation rules of i-adjectives like 'hayai' or 'oishii'.
Confusing 'fuantei' with 'fuan' (anxiety). → Use 'fuan' for feelings and 'fuantei' for states.
While related, 'fuan' is the emotion of being worried. 'Fuantei' is the objective state of being shaky or unstable.
Using 'fuantei' for physical shaking that is better described by onomatopoeia. → Use 'gura-gura' for a shaky table.
Native speakers prefer 'gura-gura' for immediate physical sensations. 'Fuantei' sounds a bit too formal or technical for a wobbly table leg in casual talk.
Saying 'fuantei no tenki'. → fuantei-na tenki.
Because it's a na-adjective, you use 'na' to connect it to a noun, not the particle 'no'.
Using 'fuantei' to mean 'dangerous' in all contexts. → Use 'abunai' for danger.
Something can be unstable (fuantei) without being immediately dangerous (abunai), and vice versa.

ヒント

Na-Adjective Rule

Always remember to add 'na' when modifying a noun. 'Fuantei isu' is wrong; it must be 'fuantei-na isu'.

Pair with 'Joutai'

If you want to sound more professional, use 'fuantei-na joutai' (unstable state) instead of just 'fuantei'.

Long 'Ei'

Make sure to hold the 'ei' sound at the end of 'fuantei' for two beats. It's 'fu-an-te-i', not 'fu-an-te'.

Weather Keywords

In weather forecasts, 'fuantei' is often followed by 'kyuuna ame' (sudden rain). Use this to prepare for the day!

Antei vs. Fuantei

In Japan, 'antei' is a major life goal. Knowing 'fuantei' helps you understand what people are trying to avoid in their careers.

Kanji Meaning

Focus on the 'Fu' (不). It's used in many words like 'fubene' (inconvenient) or 'fuan' (anxiety). It always means 'not'.

Adverb Use

Use 'ni' to turn it into an adverb: 'Fuantei ni yureru' (to shake unstably).

IT Context

If your computer is acting up, tell tech support 'Dousa ga fuantei desu' (The operation is unstable).

The Wobbly Fan

Imagine a **FAN** that is **TAY**-ing over. FU-AN-TEI. It's unstable!

Start Physical

Learn the physical meaning first (wobbly chair), then expand to weather, then to abstract things like the economy.

暗記しよう

記憶術

Think of a 'FAN' (fu-an) that is 'TAY-ing' (tei) over. The fan is unstable and about to fall!

視覚的連想

Imagine a tall stack of plates leaning precariously to one side, almost touching the floor.

Word Web

Unstable weather Wobbly chair Volatile stocks Mood swings Shaky ladder Weak internet Insecure job Political turmoil

チャレンジ

Try to find three things in your room that are 'fuantei' (like a loose cable or a pile of clothes) and say 'Kore wa fuantei desu' for each one.

語源

Composed of the Chinese characters 不 (not/un-), 安 (peace/relax/stable), and 定 (fix/decide). The compound word was formed in Japan using Chinese roots (Sino-Japanese vocabulary) to describe a lack of 'antei' (stability).

元の意味： Literally 'not fixed in peace' or 'not settled'.

Sino-Japanese (Kango)

文化的な背景

Be careful when using 'fuantei' to describe people. It is better to use it for situations or specific emotions rather than a person's entire character unless you are in a medical context.

In English, 'unstable' can sound very harsh when applied to people (implying 'crazy'). In Japanese, 'fuantei' is also serious but often used more clinically or to describe a temporary state of moodiness.

Weather reports (Tenki Yohou) use this word daily. News segments on 'Employment Instability' (Koyou Fuantei). Psychology textbooks discussing 'Joucho Fuantei' (Emotional Instability).

実生活で練習する

実際の使用場面

Weather Forecast

大気の状態が不安定 (Atmospheric state is unstable)
不安定な空模様 (Unstable sky conditions)
急な雨に注意 (Watch out for sudden rain)
雷雨の可能性 (Possibility of thunderstorms)

Mental Health

情緒不安定 (Emotional instability)
気持ちが揺れ動く (Feelings waver)
ストレスで不安定 (Unstable due to stress)
精神的なバランス (Mental balance)

Economics/Business

株価の不安定な動き (Unstable stock movements)
供給網の不安定化 (Destabilization of supply chains)
不安定な雇用 (Unstable employment)
市場の混乱 (Market turmoil)

Technology/IT

接続が不安定 (Connection is unstable)
システムの不安定動作 (Unstable system operation)
サーバーが不安定 (Server is unstable)
再起動が必要 (Restart required)

Physical Surroundings

足場が不安定 (Footing is unstable)
不安定な積み方 (Unstable way of stacking)
家具のガタつき (Rattling/shaking of furniture)
バランスを崩す (To lose balance)

会話のきっかけ

"最近、天気が不安定で、いつ雨が降るか分かりませんね。(The weather has been unstable lately, we don't know when it will rain.)"

"このテーブル、少し不安定じゃないですか？(Isn't this table a little unstable?)"

"ネットの接続が不安定なんですが、そちらはどうですか？(My internet connection is unstable; how about yours?)"

"世界情勢が不安定になると、物価が上がって困りますね。(When the world situation becomes unstable, prices go up and it's a problem.)"

"仕事が不安定な時期は、どうやってモチベーションを保っていますか？(How do you maintain motivation during times when work is unstable?)"

日記のテーマ

最近、自分の気持ちが不安定だと感じたことはありますか？その理由は何ですか？(Have you felt your feelings were unstable lately? What was the reason?)

「不安定な生活」と「安定した生活」、あなたにとってどちらが魅力的ですか？(Which is more attractive to you: an 'unstable life' or a 'stable life'?)

日本の天気について、不安定だと感じたエピソードを書いてください。(Write an episode about a time you felt the weather in Japan was unstable.)

経済が不安定な時、私たちはどのような準備をするべきだと思いますか？(What kind of preparations do you think we should make when the economy is unstable?)

今の社会で、最も「不安定」だと感じるものは何ですか？(What do you feel is the most 'unstable' thing in current society?)

よくある質問

10 問

Yes, but be careful. Using it for a person usually refers to their mental or emotional state ('joucho fuantei'). It's more common in a clinical or serious sense rather than describing someone's personality as 'quirky'. If you mean someone is moody, 'kimagure' might be better. If you mean they are actually going through a hard time, 'fuantei' is appropriate.

'Gura-gura' is an onomatopoeia used for physical shaking, like an earthquake or a wobbly table leg. It's very visual and casual. 'Fuantei' is a more formal, abstract word that covers physical, emotional, and economic instability. You would use 'gura-gura' for a loose tooth, but 'fuantei' for an unstable internet connection.

You use the word 'fuantei-ka' (不安定化) combined with 'suru' (to do). So, 'fuantei-ka suru' means 'to destabilize' or 'to become unstable'. Example: 'Jousei o fuantei-ka suru' (To destabilize the situation).

Generally, yes, because it implies a lack of balance or reliability. However, in some scientific contexts, it's just a neutral description of a state (like an unstable isotope). In daily life, nobody usually wants things to be 'fuantei'.

Absolutely! 'Setsuzoku ga fuantei' (The connection is unstable) is the standard way to describe Wi-Fi or internet that keeps cutting out or slowing down.

The opposite is 'antei' (安定), which means stability or equilibrium. You can use it in almost all the same contexts: 'antei-shita shigoto' (a stable job), 'antei-shita tenki' (stable weather), etc.

Yes, 'fuantei-na kankei' (an unstable relationship) describes a couple that breaks up and gets back together often or has a lot of conflict. It's a very common usage.

Since it's a na-adjective, just add 'na' after it: 'fuantei-na [noun]'. For example: 'fuantei-na ashiba' (unstable footing).

It means 'emotional instability'. It's often used to describe someone who is crying one minute and angry the next, or someone who is currently very stressed and sensitive.

Yes, it's a staple word in news reporting. You'll hear it constantly in reference to 'sekai jousei' (world situation), 'kabuka' (stock prices), and 'taiki' (the atmosphere/weather).

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