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B2 noun #4,500 most common 8 min read

妥当性

datousei Top 4,500

Practice it Examples Notes & Tips 妥当性 in 30 Seconds

Explanation 妥当性 in your Level:

At the A1 level, '妥当性' (datōsei) is a very difficult word that you won't usually need. It means something is 'valid' or 'makes sense' in a very serious way. Think of it like a super-formal version of 'correct' or 'okay.' While you might say 'This is okay' (Kore wa daijōbu) in daily life, a scientist would say 'This has validity' (Datōsei ga aru). You don't need to use this word yet, but if you see it in a news headline, just remember it's about something being logical or right. It's like the difference between saying 'That's a good idea' and 'That is a logically sound proposal.' For now, just focus on simple words like 'tadashii' (correct) or 'ii' (good). If you want to express that something is reasonable, 'tadashii' is your best friend. 'Datōsei' is like the boss level of 'tadashii.'

As an A2 learner, you are starting to see more complex kanji. '妥当性' (datōsei) is a word used in news or school. It means 'validity.' Imagine you are doing a science experiment. If your experiment is done the right way, it has 'datōsei.' If you just guess the answer, it doesn't have 'datōsei.' It's a noun. You will often see it as '妥当性がある' (datōsei ga aru) which means 'it is valid.' You might also see '妥当性がない' (datōsei ga nai) which means 'it is not valid.' Don't worry about using it in casual conversation with friends. If you use it while talking about a movie, people might think you are being too serious! Stick to 'tekisetsu' (appropriate) for most things, but keep an eye out for this word in formal reading materials or when someone is giving a presentation.

At the B1 level, you should begin to recognize '妥当性' (datōsei) in formal contexts like business meetings or newspaper articles. It translates to 'validity' or 'soundness.' It's an essential word for discussing theories, plans, or arguments objectively. Unlike 'tadashii' (correct), which can be subjective, 'datōsei' implies that there is a logical reason or a standard that makes something acceptable. For example, if a company sets a new price for a product, they have to explain the 'datōsei' (reasonableness/validity) of that price to their customers. You can use the pattern '～の妥当性を検討する' (examine the validity of...). This shows you are thinking critically. It's a great word to use when you want to move beyond basic Japanese and express more complex, professional thoughts.

For B2 learners, '妥当性' (datōsei) is a key vocabulary item for achieving fluency in professional and academic Japanese. You should be able to use it to discuss the integrity of data, the soundness of a legal argument, or the appropriateness of a social policy. It specifically refers to the quality of being logically or scientifically sound. You should distinguish it from '正当性' (seitōsei - legitimacy/rightfulness) and '有効性' (yūkōsei - effectiveness). In a debate, you might say, 'その主張には妥当性が欠けています' (That claim lacks validity). This sounds much more sophisticated and objective than saying 'It's wrong.' You should also be comfortable with related forms like the na-adjective '妥当な' (datō-na), meaning 'reasonable' or 'appropriate.' Mastering this word allows you to engage in high-level discussions about methodology and logic.

At the C1 level, you are expected to use '妥当性' (datōsei) with precision in nuanced contexts. You should understand its application in specific fields like psychometrics (construct validity - 構成概念妥当性), law (legal validity), and philosophy. You should be able to argue for or against the 'datōsei' of complex systems or abstract theories. At this level, you don't just know the word; you know the collocations that surround it, such as '妥当性を担保する' (to guarantee/ensure validity) or '妥当性を検証する' (to verify validity). You can use it to critique the underlying assumptions of a research paper or a corporate strategy. Your usage should reflect an understanding that 'datōsei' is about the internal logic and the external fit of a concept within its specific framework. It is a tool for high-level analytical communication.

As a C2 learner, '妥当性' (datōsei) is a word you use instinctively to navigate the most complex intellectual landscapes. You understand the subtle philosophical implications of 'validity' versus 'truth' and can articulate these differences in Japanese. You are capable of discussing the 'epistemological validity' of different knowledge systems or the 'constitutional validity' of new legislation with the same ease as a native speaker. You use the word to provide deep, structural critiques of arguments, identifying exactly where the 'datōsei' breaks down—whether it's in the premises, the methodology, or the interpretation of results. You can seamlessly weave this word into scholarly articles, legal briefs, or executive summaries, using it to build a sense of objective authority and rigorous logical standards in your Japanese discourse.

Practice it Examples Notes & Tips

妥当性 in 30 Seconds

妥当性 (datōsei) means 'validity' or 'soundness.' It is used in formal contexts like science, law, and business to describe logical correctness.
It is a noun composed of kanji for 'appropriate' (妥), 'hit/right' (当), and 'nature/quality' (性). It implies something is justifiable.
Commonly used phrases include '妥当性がある' (is valid) and '妥当性を検証する' (to verify validity). It is more formal than 'tadashii' (correct).
Avoid using it in casual conversation. It specifically refers to the logical process and evidence rather than just a simple right or wrong answer.

The Japanese term 妥当性 (datōsei) is a sophisticated noun that translates primarily as 'validity,' 'adequacy,' or 'soundness.' It is composed of three kanji characters: 妥 (gentle/appropriate), 当 (to hit/appropriate), and 性 (nature/quality). When combined, they describe the inherent quality of being logical, reasonable, and fitting for a specific context or standard. This word is not typically used in casual daily chatter about what to eat for lunch; rather, it resides in the realms of academic research, legal discourse, high-level business strategy, and scientific inquiry. It measures whether a conclusion, a method, or a judgment holds water when scrutinized against logic or empirical evidence.

Logical Soundness: In logic, it refers to the property where a conclusion follows necessarily from its premises. If an argument is 'datō,' it means the reasoning is solid and cannot be easily dismissed.

Scientific Validity: In research, this word is used to discuss whether a test actually measures what it claims to measure. For example, does an IQ test truly measure intelligence? This is a question of its '妥当性'.

この調査結果の妥当性を疑う余地はない。(There is no room to doubt the validity of these survey results.)

Understanding the nuance of datōsei requires distinguishing it from simple 'correctness' (正解 - seikai) or 'truth' (真実 - shinjitsu). While something can be 'true' by accident, 'validity' implies a systematic appropriateness. If a judge makes a ruling based on the law, the ruling has datōsei because it follows the established legal framework, even if some people disagree with the outcome. It is about the process and the justification as much as the result.

その計画には経済的な妥当性が認められない。(Economic validity is not recognized in that plan.)

In business contexts, you will often hear this word during the evaluation phase of a project. When a manager asks, 'Is this budget valid?' they are asking for the datōsei of the numbers. They want to know if the numbers are backed by data and realistic projections. It suggests a level of scrutiny that goes beyond just 'is it okay?' to 'is it justifiable?'

Social Acceptability: Sometimes used to describe whether an action is appropriate given social norms and expectations, though '適切' (tekisetsu) is more common for general behavior.

Using 妥当性 (datōsei) effectively involves understanding its grammatical role as a noun. It often acts as the subject of a sentence or the object of a verb related to analysis. Because it is a formal word, the surrounding grammar should ideally match this level of politeness or technicality. You will frequently see it paired with the particle 'を' (wo) when someone is examining or questioning validity, or 'が' (ga) when validity is being described as existing or lacking.

専門家チームが、新薬の治験データの妥当性を厳しくチェックしている。(A team of experts is strictly checking the validity of the clinical trial data for the new drug.)

One of the most common patterns is [Noun] の妥当性. This allows you to specify exactly what kind of validity you are talking about. For instance, '論理的妥当性' (ronriteki datōsei) means logical validity, while '統計的妥当性' (tōkeiteki datōsei) means statistical validity. This precision is vital in scientific writing and formal reports.

Pattern: 妥当性を欠く (datōsei wo kaku): This means 'to lack validity.' It is a very common way to criticize an argument or a proposal politely but firmly in a professional setting.

その主張は根拠が薄く、妥当性に欠けると判断された。(That claim was judged to lack validity because the evidence was weak.)

Another important usage is in the phrase 妥当性が認められる (datōsei ga mitomerareru), which translates to 'validity is recognized.' This is the 'green light' phrase in bureaucratic or legal contexts. It signifies that after careful review, the subject has been found to be sound and acceptable.

Pattern: 妥当性を検証する (datōsei wo kenshō suru): Meaning 'to verify the validity.' This is the standard procedure for any scientific experiment or policy review.

このアルゴリズムの妥当性を数学的に証明する必要がある。(It is necessary to mathematically prove the validity of this algorithm.)

In contemporary Japan, 妥当性 (datōsei) is a staple of news broadcasts, particularly when discussing government policies, legal rulings, or scientific breakthroughs. When the Diet (Japan's parliament) debates a new tax law, opposition members will frequently question the datōsei of the proposed figures. You will hear it in the mouth of news anchors providing commentary on the 'reasonableness' of a court's decision in a high-profile case.

Academic Lectures: University students in the social sciences or STEM fields will encounter this word daily. Professors use it to discuss the integrity of research methodologies and the strength of theoretical frameworks.

「この実験手法の妥当性について、皆さんはどう考えますか？」(What do you all think about the validity of this experimental method?)

In the corporate world, specifically during board meetings or project post-mortems, datōsei is the yardstick for accountability. When a project fails, the post-mortem often focuses on whether the initial assumptions had datōsei. If a company is being audited, the auditors are essentially checking the datōsei of the financial statements to ensure they reflect the true state of the business.

Legal Contexts: Lawyers use this word to argue whether a piece of evidence should be admitted or whether a contract's terms are fair and reasonable under the law.

裁判所は、その解雇の妥当性を認めた。(The court recognized the validity of that dismissal.)

Finally, in the field of Information Technology, specifically in data science and AI, the datōsei of training data is a hot topic. Engineers discuss whether the data used to train a model is 'valid' for the real-world application it is intended for. This usage bridges the gap between traditional logic and modern technology.

One of the most frequent mistakes learners make with 妥当性 (datōsei) is using it in contexts that are too casual. Because it is a highly formal, abstract noun, using it to describe something mundane like the 'validity' of a sandwich choice or a movie preference sounds unnaturally stiff or even slightly sarcastic. For everyday 'appropriateness,' words like 適切 (tekisetsu) or ちょうどいい (chōdo ii) are much better fits.

Confusing with 'Correctness' (正解): Learners often use '妥当性' when they simply mean 'is it the right answer?'. 妥当性 is about the *reasoning* and *logic*, not just the binary outcome of right vs. wrong.

Incorrect: この数学の問題の妥当性は何ですか？ (What is the validity of this math problem?)
Correct: この数学の問題の正解は何ですか？ (What is the correct answer to this math problem?)

Another error involves the grammatical structure. Since it is a noun ending in '性' (-ity/-ness), it cannot be used directly as an adjective. You cannot say '妥当性な判断' (a validity judgment). You must either use it as a noun ('妥当性の検証') or use the 'na-adjective' form 妥当な (datō-na) to modify a noun directly.

Confusing with 'Effectiveness' (有効性): '有効性' (yūkōsei) means something works and produces results. '妥当性' means something is logical and appropriate. A medicine might be 'validly' (妥当) prescribed but not 'effective' (有効) for a specific patient.

その対策の妥当性（論理的な正しさ）と有効性（実際の効果）の両方を検討すべきだ。(We should examine both the validity [logical correctness] and effectiveness [actual effect] of that measure.)

Finally, be careful with the particle usage. While '妥当性がある' (there is validity) is correct, learners sometimes mistakenly say '妥当性にする' (to make it validity), which is nonsensical. If you want to say 'to make it valid,' you would use '妥当なものにする' or '妥当性を確保する' (to ensure validity).

To truly master 妥当性 (datōsei), you must see how it sits alongside its linguistic cousins. Japanese has many words for 'correctness' and 'appropriateness,' each with a specific flavor. Choosing the right one shows a high level of fluency.

正当性 (Seitōsei) - Legitimacy: While '妥当性' is about logic and reason, '正当性' is about being 'right' in a moral, legal, or authoritative sense. A king has '正当性' (legitimacy) to rule; a scientific theory has '妥当性' (validity).

適切さ (Tekisetsusa) - Appropriateness: This is a more general, less academic word. It refers to something being 'fitting' for a situation. Choosing the 'appropriate' (適切) tie for a wedding is a social matter, not a question of logical 'validity' (妥当性).

「その表現は、この場では適切ではない」と言いますが、「この論理は妥当性に欠ける」と言います。(We say 'that expression is not appropriate [tekisetsu] in this setting,' but we say 'this logic lacks validity [datōsei].')

Another alternative is 合理的 (gōriteki), meaning 'rational' or 'logical.' While '妥当性' is the noun form of 'validity,' '合理的' is often used as an adjective to describe a person's thinking process. '彼の考えは合理的だ' (His thinking is rational). You could say his thinking has datōsei, but gōriteki focuses more on the efficiency and logic of the thought itself.

信憑性 (Shinpyōsei) - Credibility: This refers to how 'believable' or 'trustworthy' something is. A witness's testimony is checked for '信憑性'. If the testimony is 'valid' in the sense that it fits the known facts, it might also have '妥当性', but the focus is on trust.

In summary, choose 妥当性 for: logic, scientific methods, legal standards, and formal justifications. Use its synonyms for: moral rightness (正当性), social fit (適切さ), or trustworthiness (信憑性).

How Formal Is It?

Fun Fact

The kanji '妥' (da) is also used in '妥協' (dakyō), which means compromise. Both words share the root idea of finding a 'fitting' or 'settled' point between different sides.

Pronunciation Guide

UK dä.toː.seː

US dɑ.toʊ.seɪ

Japanese is a pitch-accent language. In 'datōsei', the pitch typically rises on 'tō' and stays relatively high through 'sei'.

Rhymes With

可能性 (kanōsei - possibility) 安全性 (anzensei - safety) 必要性 (hitsuyōsei - necessity) 重要性 (jūyōsei - importance) 正確性 (seikakusei - accuracy) 多様性 (tayōsei - diversity) 信頼性 (shinraisei - reliability) 生産性 (seisansei - productivity)

Common Errors

Pronouncing 'sei' like the English word 'sea'. It should be 'say'.
Making the 'o' in 'tō' too short. It must be a double vowel length.
Stressing the first syllable 'da' like an English word. Keep it flat.
Confusing 'datō' with 'tatō' (which means many/various).
Mispronouncing '妥' (da) as 'ta'.

Difficulty Rating

Reading 4/5

The kanji are N2-N1 level, and the word is common in academic texts.

Writing 4/5

Writing '妥' can be tricky for beginners.

Speaking 3/5

The pronunciation is straightforward, but the context must be right.

Listening 3/5

Common in news and lectures, so intermediate learners will hear it often.

What to Learn Next

Prerequisites

正しい (Tadashii) 適当 (Tekitō) 理由 (Riyū) 計画 (Keikaku) 調査 (Chōsa)

Learn Next

正当性 (Seitōsei) 有効性 (Yūkōsei) 客観的 (Kyakkanteki) 検証 (Kenshō) 論理 (Ronri)

Advanced

帰納的 (Kinōteki - Inductive) 演繹的 (En'ekiteki - Deductive) 蓋然性 (Gaizensei - Probability) 整合性 (Seigōsei - Consistency)

Grammar to Know

Noun + の + 妥当性

計画の妥当性を確認する。

妥当性 + がある/ない

その意見には妥当性がない。

妥当性 + を + Verb (検証する/疑う/認める)

データの妥当性を検証する。

～としての妥当性

証拠としての妥当性が問われている。

妥当性 + に + 欠ける

彼の論理は妥当性に欠けている。

Examples by Level

この答えは、妥当性がありますか。

Is this answer valid?

Simple question using 'ga arimasu ka'.

妥当性をチェックします。

I will check the validity.

Using 'wo' to show the object of checking.

それは妥当性がないです。

That has no validity.

Negative form 'nai desu'.

データの妥当性を見ます。

I look at the validity of the data.

Noun + no + Noun structure.

妥当性は大切です。

Validity is important.

Topic marker 'wa' with an adjective 'taisetsu'.

もっと妥当性がほしいです。

I want more validity.

Using 'hoshii' to express desire.

妥当性を考えてください。

Please think about the validity.

Polite request 'kudasai'.

妥当性はどこですか。

Where is the validity?

Question word 'doko'.

その計画の妥当性を確認してください。

Please confirm the validity of that plan.

Confirm (kakunin) used with 'wo'.

このテストには妥当性があります。

This test has validity.

Indicating existence with 'ga arimasu'.

彼の意見には妥当性がありません。

There is no validity in his opinion.

Showing lack of something with 'ga arimasen'.

妥当性を調べるのは難しいです。

Investigating validity is difficult.

Nominalizing the verb 'shiraberu' with 'no'.

もっと妥当性のある説明が必要です。

A more valid explanation is necessary.

'Datōsei no aru' acts as an adjective phrase.

妥当性を証明するのはあなたの仕事です。

Proving the validity is your job.

Topic marker 'wa' after a nominalized verb.

そのニュースの妥当性を疑っています。

I doubt the validity of that news.

Continuous form 'utagatte imasu'.

妥当性を高めるために、調査をしました。

In order to increase validity, I conducted a survey.

Using 'tame ni' to show purpose.

研究の妥当性を保証するために、多くのサンプルを集めた。

To guarantee the validity of the research, I collected many samples.

Using 'hoshō suru' (guarantee).

その主張の妥当性について議論しましょう。

Let's discuss the validity of that claim.

Using 'ni tsuite' (about/concerning).

この予算案は妥当性に欠けていると思います。

I think this budget proposal lacks validity.

The phrase 'kakeru' means to lack.

妥当性が認められれば、プロジェクトは進みます。

If the validity is recognized, the project will proceed.

Conditional 'reba' form.

専門家は、そのデータの妥当性を高く評価した。

The expert highly evaluated the validity of that data.

Adverb 'takaku' modifying 'hyōka shita'.

妥当性を検証するプロセスが不十分だった。

The process of verifying validity was insufficient.

Using 'fujūbun' (insufficient).

この理論の妥当性は、まだ証明されていない。

The validity of this theory has not been proven yet.

Passive negative potential 'shōmei sarete inai'.

妥当性を問われる場面が増えている。

The number of situations where validity is questioned is increasing.

Passive form 'towareru' (to be questioned).

新薬の臨床試験における妥当性を厳密に審査する。

We will strictly examine the validity in the clinical trials of the new drug.

Using 'genmitsu ni' (strictly).

その判決の妥当性に対して、世論が分かれている。

Public opinion is divided over the validity of that verdict.

Using 'taishite' (towards/regarding).

統計的な妥当性を確保するため、無作為抽出を行った。

To ensure statistical validity, we performed random sampling.

Using 'kakuho suru' (to ensure/secure).

論理的な妥当性だけでなく、倫理的な側面も考慮すべきだ。

We should consider not only logical validity but also ethical aspects.

Using 'dake de naku' (not only).

その仮説の妥当性を裏付ける証拠が見つかった。

Evidence that supports the validity of that hypothesis was found.

Using 'urazukeru' (to support/back up).

妥当性を疑う根拠は、今のところ見当たらない。

At the moment, there is no basis to doubt the validity.

Using 'miataranai' (cannot be found).

この手法の妥当性については、再考の余地がある。

Regarding the validity of this method, there is room for reconsideration.

The phrase 'yochi ga aru' means there is room for.

妥当性を維持しつつ、コストを削減する方法を探る。

We seek ways to reduce costs while maintaining validity.

Using 'tsutsu' (while doing).

政策の妥当性を評価する基準を明確に定めるべきである。

The criteria for evaluating the validity of policies should be clearly defined.

Using 'beki de aru' (should).

構成概念妥当性の欠如が、研究結果の信頼性を損なっている。

A lack of construct validity is undermining the reliability of the research results.

Using 'sonnatte iru' (undermining/damaging).

この契約条項は、法的な妥当性を有していると言えるだろうか。

Could it be said that this contract clause possesses legal validity?

Using 'yushite iru' (possess/have).

妥当性をめぐる議論は、最終的に哲学的な問いに行き着いた。

The debate surrounding validity eventually reached a philosophical question.

Using 'meguru' (surrounding/concerning).

アルゴリズムの妥当性を数学的に厳密に定義する必要がある。

It is necessary to mathematically and strictly define the validity of the algorithm.

Using 'teigi suru' (to define).

既存の枠組みにおける妥当性を超えた、新しい視点が求められている。

A new perspective is required that goes beyond validity within existing frameworks.

Using 'koeta' (exceeded/beyond).

その理論の妥当性は、多くの反証によって覆された。

The validity of that theory was overturned by many counter-evidences.

Passive form 'fukusa reta' (was overturned).

妥当性の検証を怠ることは、科学者としての責任放棄に等しい。

Neglecting the verification of validity is equivalent to abandoning one's responsibility as a scientist.

Using 'ni hitoshii' (equivalent to).

本研究の主眼は、言説分析における妥当性の再構築にある。

The main focus of this research lies in the reconstruction of validity in discourse analysis.

Formal structure 'shugan wa ... ni aru'.

認識論的妥当性を欠いた言説は、単なるドグマに過ぎない。

Discourse lacking epistemological validity is nothing more than mere dogma.

Using 'ni suginai' (nothing more than).

その法律の憲法適合性、ひいては妥当性が最高裁で争われた。

The constitutionality, and by extension the validity, of that law was contested in the Supreme Court.

Using 'hiite wa' (and by extension).

主観的な経験に客観的な妥当性を付与することは可能か。

Is it possible to grant objective validity to subjective experiences?

Using 'fuyo suru' (to grant/bestow).

妥当性のパラダイムがシフトする中で、我々は新たな基準を模索している。

As the paradigm of validity shifts, we are searching for new criteria.

Using 'mosaku shite iru' (searching/groping for).

その論証の妥当性は、自明の理として受け入れられてきた。

The validity of that demonstration had been accepted as a self-evident truth.

Using 'jimei no ri' (self-evident truth).

妥当性を担保するための重層的な検証プロセスを導入した。

We introduced a multi-layered verification process to ensure validity.

Using 'jūsōteki na' (multi-layered).

普遍的な妥当性を標榜する理論ほど、個別の事象を軽視しがちである。

The more a theory advocates for universal validity, the more it tends to neglect individual phenomena.

Using 'hyōbō suru' (to advocate/claim).

Synonyms

正当性適切さ確実性合理性有効性

Antonyms

不当性不合理

Common Collocations

妥当性を検証する

妥当性に欠ける

妥当性が認められる

妥当性を確保する

妥当性を疑う

論理的妥当性

統計的妥当性

妥当性を審査する

経済的妥当性

妥当性を担保する

Common Phrases

妥当性の高い

— Highly valid or very reasonable. Often used to describe research or a plan.

これは妥当性の高いデータだ。

妥当性の低い

— Lacking validity or being unreasonable. Used to criticize weak arguments.

妥当性の低い主張だ。

妥当性を問う

— To question the validity of something. Used in debates or critical reviews.

政府の方針の妥当性を問う。

妥当性を吟味する

— To carefully scrutinize or examine the validity. Implies a deep, careful check.

証言の妥当性を吟味する。

妥当性を裏付ける

— To support or provide evidence for the validity of something.

新しい事実が妥当性を裏付けた。

妥当性を欠いた

— Lacking validity (adjectival phrase). Describes something that is already judged as invalid.

妥当性を欠いた判断だ。

妥当性を追求する

— To seek or pursue validity. Often used in scientific or philosophical contexts.

真理と妥当性を追求する。

妥当性を認める

— To acknowledge or accept the validity of something.

裁判所は彼の言い分の妥当性を認めた。

妥当性を再考する

— To reconsider the validity of something. Used when new information comes to light.

旧来の手法の妥当性を再考する。

妥当性を評価する

— To evaluate the validity. A standard step in many professional processes.

プロジェクトの妥当性を評価する。

Often Confused With

妥当性 vs 正当性 (Seitōsei)

Seitōsei is about legitimacy or moral rightness, while Datōsei is about logical validity.

妥当性 vs 有効性 (Yūkōsei)

Yūkōsei is about effectiveness (does it work?), while Datōsei is about soundness (is it logical?).

妥当性 vs 適切 (Tekisetsu)

Tekisetsu is a general word for 'appropriate,' while Datōsei is much more formal and analytical.

Idioms & Expressions

"妥当性を欠く"

— To lack validity or logic. This is the most common 'idiomatic' usage in professional speech.

その説明は妥当性を欠いている。

Formal

"妥当性を担保する"

— To provide a guarantee for validity. 'Tanpo' originally means collateral in finance.

第三者機関が妥当性を担保する。

Very Formal/Legal

"妥当性を疑う余地はない"

— There is no room to doubt the validity. Used to express strong confidence.

この結果の妥当性を疑う余地はない。

Formal/Literary

"妥当性の検証に耐える"

— To withstand verification of validity. Means the idea is very strong.

この理論は厳格な妥当性の検証に耐える。

Academic

"妥当性を盾に取る"

— To use validity as a shield/excuse. (Less common, but possible in critical contexts).

彼は論理的妥当性を盾に取って、他人の感情を無視した。

Formal/Critical

"妥当性の壁"

— The barrier of validity. Referring to the difficulty of proving something is sound.

新しいアイデアが妥当性の壁にぶつかる。

Figurative

"妥当性をはき違える"

— To misunderstand what validity means in a specific context.

彼は科学的妥当性と個人的な好みをはき違えている。

Formal/Critical

"妥当性を棚上げにする"

— To set aside the question of validity for a moment.

妥当性は棚上げにして、まずは実行してみよう。

Business/Informal

"妥当性に光を当てる"

— To shine a light on the validity of something. To focus on it.

この研究は、古くからある慣習の妥当性に光を当てた。

Literary

"妥当性を突き詰める"

— To investigate validity to its very end/limit.

議論を重ねて妥当性を突き詰める。

Formal

Easily Confused

妥当性 vs 適当 (Tekitō)

Both share the kanji '当' and mean 'appropriate.'

Tekitō is often used casually to mean 'random' or 'half-hearted,' whereas Datōsei is strictly formal and implies rigorous logic.

適当に返事をする (Give a random/half-hearted reply) vs 妥当性を検証する (Verify validity).

妥当性 vs 妥協 (Dakyō)

Both share the kanji '妥'.

Dakyō means 'compromise' (giving up something to agree), while Datōsei means 'validity' (being logically sound).

妥協案を探る (Look for a compromise) vs 妥当性を検討する (Examine validity).

妥当性 vs 妥結 (Daketsu)

Both share the kanji '妥'.

Daketsu means 'reaching an agreement' (like a union and management), while Datōsei is a quality of an argument.

交渉が妥結した (Negotiations reached an agreement) vs 主張の妥当性 (Validity of a claim).

妥当性 vs 納得 (Nattoku)

Both relate to things making sense.

Nattoku is a personal feeling of being convinced, while Datōsei is an objective quality of being logical.

彼の説明に納得した (I was convinced by his explanation) vs 説明の妥当性 (The validity of the explanation).

妥当性 vs 正確性 (Seikakusei)

Both relate to being 'right.'

Seikakusei is 'accuracy' (no errors), while Datōsei is 'validity' (logical soundness). A clock can be accurate (seikaku) but its use in a specific experiment might not have validity (datōsei).

データの正確性 (Accuracy of data) vs データの妥当性 (Validity of data).

Sentence Patterns

[Noun] の妥当性は [Adjective] です。

この計画の妥当性は高いです。

[Noun] には妥当性が [ある/ない] と思います。

彼の意見には妥当性がないと思います。

[Noun] の妥当性を [Verb] する。

ニュースの妥当性を確認する。

[Noun] は妥当性に欠けている。

その主張は妥当性に欠けている。

妥当性を担保するために [Action]。

妥当性を担保するために、専門家に相談した。

[Noun] における妥当性を [Verb]。

法廷における証拠の妥当性を審査する。

妥当性を疑う余地はない。

研究結果の妥当性を疑う余地はない。

妥当性を標榜する [Noun]。

普遍的な妥当性を標榜する理論。

Word Family

Nouns

妥当 (Datō - appropriateness/validity)

正当性 (Seitōsei - legitimacy)

有効性 (Yūkōsei - effectiveness)

不当 (Futō - injustice/unfairness)

Verbs

妥当する (Datō suru - to be valid/applicable - rare, usually as an adjective)

Adjectives

妥当な (Datō-na - valid/reasonable/appropriate)

不当な (Futō-na - unfair/unjust)

妥協 (Dakyō - compromise)

妥結 (Daketsu - reaching an agreement)

相当 (Sōtō - considerable/equivalent)

適当 (Tekitō - suitable/random)

該当 (Gaitō - corresponding/falling under)

How to Use It

frequency

Common in formal writing, news, and professional environments. Rare in casual daily life.

Common Mistakes

Using '妥当性' for everyday correctness. → Use '正しい' or '合っている'.
You wouldn't say your shopping list has '妥当性'. That's too formal.
Saying '妥当性な判断'. → Say '妥当な判断'.
You cannot use a noun with '-na' to make an adjective. Use the proper adjective form.
Confusing '妥当性' with '有効性'. → Use '有効性' for effectiveness.
A plan can be 'valid' (logical) but not 'effective' (it doesn't work).
Using '妥当性' to mean 'truth'. → Use '真実' or '事実'.
Validity is about the logic and reasoning, not necessarily the ultimate truth.
Pronouncing it as 'dätosei' (short o). → Pronounce it as 'dätōsei' (long o).
Length of vowels is crucial in Japanese for understanding.

Tips

Noun vs Adjective

Remember that '妥当性' is a noun. Use '妥当な' when you need an adjective to modify another noun directly. E.g., '妥当な理由' (a valid reason).

Kanji Breakdown

Focus on the kanji '妥' (appropriate/peace). It's the key to several formal words like 妥協 (compromise) and 妥結 (agreement).

Business Etiquette

In a Japanese meeting, if you want to disagree with a proposal politely, say 'その計画の妥当性について、少し懸念があります' (I have some concerns about the validity of that plan).

Research Papers

If you are writing a paper in Japanese, use '妥当性' to discuss your methodology. It is the standard term for 'validity' in all scientific fields.

News Keywords

When listening to the news, 'datōsei' is often followed by 'wo towarete iru' (is being questioned). This is a common phrase when a government action is controversial.

Data-Target-Nature

Break down the sounds: DA (Data) - TO (Target) - SEI (Nature). The nature of data hitting the target is its validity.

Particle Choice

Use '妥当性を' with action verbs like check or verify. Use '妥当性が' with state verbs like exist (aru) or be recognized (mitomerareru).

Logic vs Truth

Something can be logically 'valid' (datō) within a system even if the starting point is wrong. It's about the internal consistency.

Professional Tone

Using 'datōsei' automatically elevates your speech to a professional level. Use it when you want to be taken seriously.

Legal Texts

In legal Japanese, '妥当性' often refers to the 'reasonableness' of an action under the law. It's a key term for law students.

Memorize It

Mnemonic

Think of 'DA' as 'DATA' and 'TO' as 'TOTAL.' If your 'DATA' is 'TOTAL-ly' right, it has 'Datōsei' (Validity).

Visual Association

Imagine a judge hitting a gavel (当) on a very peaceful (妥) looking document. The 'nature' (性) of this act is 'Datōsei'—validity.

Word Web

Logic Research Reasonable Legal Scientific Soundness Evidence Appropriate

Challenge

Try to find one news article today in a Japanese newspaper (like Asahi or Mainichi) that uses the word 妥当性. Write down the context in which it was used.

Word Origin

The word is a Sino-Japanese compound (Kango). '妥' (da) originally meant a hand over a woman, signifying peace or settling things down. '当' (tō) means to hit a target or be right. '性' (sei) is a suffix meaning 'nature' or 'quality.'

Original meaning: The quality of things being settled correctly and hitting the mark of truth or reason.

Japonic (Sino-Japanese vocabulary)

Cultural Context

This is a neutral, formal word. It is never offensive, but using it in an emotional argument can make you seem cold or overly analytical.

In English, we might use 'validity' mainly in science, but 'reasonableness' in law. Japanese uses '妥当性' for both.

Used frequently in the 'Japanese Civil Code' (Minpō) discussions. A key term in the 'Japanese Industrial Standards' (JIS) for quality control. Often used in the 'White Paper on the Police' to justify law enforcement actions.

Practice in Real Life

Real-World Contexts

Scientific Research

実験の妥当性
データの妥当性
妥当性を検証する
内的妥当性

Business Meetings

予算の妥当性
計画の妥当性
妥当性を検討する
妥当性が認められる

Legal/Court

判決の妥当性
処分の妥当性
妥当性を争う
法的な妥当性

Academic Writing

理論の妥当性
論理的妥当性
妥当性を担保する
妥当性を評価する

News/Politics

政策の妥当性
発言の妥当性
妥当性を問う
妥当性に欠ける

Conversation Starters

"「この新しいルールの妥当性について、どう思いますか？」 (What do you think about the validity of this new rule?)"

"「そのデータの妥当性を証明するには、何が必要でしょうか？」 (What would be needed to prove the validity of that data?)"

"「この予算案は、今の状況で妥当性があると言えますか？」 (Can it be said that this budget proposal is valid in the current situation?)"

"「専門家がその理論の妥当性を疑っているそうですね。」 (I heard that experts are doubting the validity of that theory, right?)"

"「この調査方法の妥当性を高めるためのアドバイスをください。」 (Please give me advice on how to increase the validity of this survey method.)"

Journal Prompts

今日聞いたニュースの中で、『妥当性がない』と感じたものはありましたか？その理由を書いてください。

自分の仕事や勉強の進め方の妥当性を、客観的に評価してみましょう。

『正しいこと』と『妥当性があること』の違いについて、あなたの意見を日本語で書いてください。

あなたが最近立てた計画には、十分な妥当性がありましたか？後から振り返って考えてみましょう。

社会のルールのいくつかが、今の時代に妥当性を欠いていると思いますか？具体例を挙げて説明してください。

Frequently Asked Questions

10 questions

Use '妥当性' in formal, professional, or academic settings where you are talking about the logic, methodology, or reasoning behind something. Use '正しい' in daily life for simple facts like '2+2=4' or 'that's the right way to the station.' '妥当性' is about whether something is *justifiable* based on a standard.

Rarely. If you use it with friends while deciding where to eat, it will sound like you are a robot or a very stiff professor. However, if you are discussing a serious social issue or a business plan with friends, it might be used, but it's still quite formal.

Think of '妥当性' (datōsei) as 'logical validity' and '正当性' (seitōsei) as 'moral or legal legitimacy.' For example, a lawyer might argue that a search was 'valid' (datō) based on logic, but a politician might argue their right to rule has 'legitimacy' (seitōsei).

No. '妥当性' is a noun. If you want an adjective, use '妥当な' (datō-na). For example: '妥当な判断' (a valid judgment) or '妥当な価格' (a reasonable price).

It means 'to lack validity.' It is a very common and polite way to say that an argument, theory, or plan does not make sense or is not well-supported by logic/facts.

In science, it refers to whether a test measures what it intends to measure. You would say '実験の妥当性を検証する' (verify the validity of the experiment) or talk about '内的妥当性' (internal validity).

Yes, it is typically considered an N1 level word, but it can appear in N2 reading sections as well. It is essential for anyone aiming for professional-level Japanese.

Common verbs include: 検証する (verify), 検討する (examine), 疑う (doubt), 認める (recognize), 担保する (guarantee), and 評価する (evaluate).

No, it is used for ideas, plans, methods, and arguments. To describe a person's suitability for a job, you would use '適格性' (tekikakusei) or simply say 'ふさわしい' (fusawashii).

The direct opposite is '不当性' (futōsei), meaning injustice or lack of proper basis. You could also say '妥当性の欠如' (lack of validity).