This page in your language

فارسی

العربية

Deutsch

Español

Français

日本語

한국어

Português

中文

हिन्दी

B2 noun #4,500 most common 9 min read

正当性

seitōsei Top 4,500

Practice it Examples Notes & Tips 正当性 in 30 Seconds

Explanation 正当性 in your Level:

At the A1 level, the word '正当性' (seitōsei) is very advanced and you won't usually need it. However, you can start by learning the first part, '正' (sei), which means 'correct' or 'right.' You might see it in '正しい' (tadashii), which is the basic word for 'correct.' At this stage, think of '正当性' as a very fancy way to say 'being right.' You won't hear it in daily greetings, but you might see it in headlines. Just remember it relates to the idea of rules and what is allowed. If you play a game and someone follows the rules, they are being 'correct.' Later, you will learn that '正当性' is the official word for this 'correctness' in law or government. For now, focus on simpler words like 'いい' (good) or 'だめ' (no good) to express if something is okay or not.

At the A2 level, you might encounter '正当' (seitō) in compound words like '正当な理由' (seitō na riyū), which means 'a good/valid reason.' If you are late to class, your teacher might ask for a 'seitō na riyū.' The word '正当性' (seitōsei) is the noun version, meaning 'the quality of being valid.' You might hear it in simple news stories about fair play or rules. It's helpful to know that '性' (sei) at the end of a word often turns it into an abstract noun, like '-ity' or '-ness' in English. So, 'seitō' (justifiable) + 'sei' (quality) = 'justifiability.' You don't need to use it in your own speaking yet, but recognizing it in a text about rules or social studies will help you understand that the topic is about what is officially considered 'right.'

At the B1 level, you should begin to understand '正当性' (seitōsei) as 'legitimacy.' This word appears when discussing social issues, history, or formal debates. For example, if you are reading about a historical event, the text might discuss the '正当性' of a king's claim to the throne. You can use it in your writing when you want to sound more professional. Instead of saying 'He was right to do that,' you could say 'His actions had legitimacy' (彼の行為には正当性があった). This level is about moving from personal opinions ('I think it's right') to objective analysis ('Is there a logical or legal basis for this?'). You should be able to distinguish it from '正確性' (seikakusei - accuracy). Remember: 'Seitōsei' is about authority and justice; 'Seikakusei' is about numbers and facts.

At the B2 level, '正当性' (seitōsei) is a key vocabulary item. You are expected to use it in discussions about politics, law, and ethics. You should know common collocations like '正当性を疑う' (to doubt the legitimacy) and '正当性を主張する' (to claim legitimacy). At this level, you understand that 'seitōsei' is not just about being 'correct,' but about having the 'right' to do something according to a system of rules or morals. You might use it in a debate about corporate ethics or government policy. You should also be able to explain the difference between '正当性' (legitimacy) and '妥当性' (validity/appropriateness). For example, a scientific method must have '妥当性' (datōsei) to be scientifically sound, but a government must have '正当性' (seitōsei) to be accepted by the people. This is a word that adds significant weight and formality to your arguments.

At the C1 level, you should have a nuanced command of '正当性' (seitōsei). You can use it to discuss complex philosophical concepts like 'procedural legitimacy' (手続き的正当性) or 'traditional legitimacy' (伝統的正当性). You will encounter it in legal documents, high-level political analysis, and philosophical treatises. You should be able to use the word to critique systems of power. For instance, you might analyze how a regime maintains its '正当性' through propaganda or legal reform. You should also be comfortable using it as a tool for logical deconstruction in academic writing. At this level, you understand that '正当性' is often a contested concept—what one group sees as legitimate, another may see as illegitimate. You can engage in deep discussions about the 'crisis of legitimacy' (正当性の危機) in modern institutions.

At the C2 level, '正当性' (seitōsei) is a fundamental concept that you use with the precision of a native speaker or a scholar. You are familiar with its use in various specialized fields, from constitutional law to sociology and international relations. You can discuss the evolution of the concept of 'seitōsei' in Japanese history, such as the 'seitōsei' of the Emperor system or the post-war constitution. You can effortlessly switch between '正当性' and its synonyms like '正統性' (seitōsei - note the different kanji for 'tō', meaning 'orthodoxy' or 'lineage'), understanding the subtle shift from 'justifiability' to 'traditional lineage.' You use the word to articulate sophisticated arguments about the moral foundations of society and the philosophical justifications for the exercise of power. Your use of the word is indistinguishable from that of a highly educated native professional.

Practice it Examples Notes & Tips

正当性 in 30 Seconds

正当性 (seitōsei) means legitimacy or validity in a formal, legal, or moral sense.
It is used to describe actions, laws, or claims that are justified by rules or authority.
Commonly heard in news, law, and business contexts rather than daily casual conversation.
Key verbs include 'proving' (shōmei), 'doubting' (utagau), and 'claiming' (shuchō) legitimacy.

The Japanese word 正当性 (seitōsei) is a sophisticated noun that translates primarily to 'legitimacy,' 'validity,' or 'justifiability.' It is composed of three kanji characters: 正 (sei) meaning 'correct' or 'righteous,' 当 (tō) meaning 'appropriate' or 'to hit the mark,' and 性 (sei) which functions as a suffix meaning 'nature' or 'quality.' When combined, they describe the quality of an action, a claim, or a system being grounded in law, ethics, or logic. This word is not typically used for casual 'rightness' (like getting a math problem right); instead, it carries significant weight in legal, political, and academic contexts. It asks the fundamental question: 'Does this person or entity have the rightful authority or a logical basis to do what they are doing?'

Legal Context: In law, 正当性 refers to the legal validity of a claim or the justification for an action, such as self-defense (正当防衛 - seitō bōei).

Political Context: In politics, it often refers to the legitimacy of a government or a ruler—whether the people recognize their right to hold power.

その支配の正当性を疑う声が上がっている。(Sono shihai no seitōsei o utagau koe ga agatte iru.) - Voices are rising that doubt the legitimacy of that rule.

Understanding the nuance of 正当性 requires recognizing that it is often used when a conflict of interest exists. If someone challenges your decision, you would argue for its 正当性 by providing evidence, precedents, or moral reasoning. It is the 'shield' of justification. In business, if a company fires an employee, they must demonstrate the 正当性 of that termination to avoid legal repercussions. In everyday life, while rare, you might hear it when people debate the fairness of a rule or a social norm. It is inherently a formal word, signaling that the speaker is engaging in a serious evaluation of rights and wrongs based on established standards rather than personal feelings.

彼の主張には一定の正当性がある。(Kare no shuchō ni wa ittei no seitōsei ga aru.) - There is a certain level of validity to his claim.

Using 正当性 (seitōsei) correctly involves pairing it with specific verbs and particles that highlight its role as a quality or a concept. Because it is a noun, it often acts as the object of a sentence (followed by を) or the subject (followed by が or は). The most common verbs associated with it are utagau (to doubt), shuchō suru (to assert/claim), mitomeru (to recognize/admit), and tou (to question/call into account). For example, if you are questioning the legitimacy of a new tax, you would use '正当性を問う' (seitōsei o tou). If you are defending your actions in a report, you would write '正当性を主張する' (seitōsei o shuchō suru).

The Verb 'To Have': When stating that something is legitimate, use '正当性がある' (seitōsei ga aru). To say it lacks it, use '正当性を欠く' (seitōsei o kaku).

武力行使の正当性を証明するのは難しい。(Buryoku kōshi no seitōsei o shōmei suru no wa muzukashii.) - It is difficult to prove the legitimacy of the use of force.

In academic writing, 正当性 is frequently used with the particle 'の' to qualify other nouns. For instance, '正当性の危機' (seitōsei no kiki) refers to a 'crisis of legitimacy,' a term often used in political science to describe a government losing the trust of its citizens. Another common structure is '[Noun] + としての正当性' (as a [Noun], its legitimacy). For example, 'リーダーとしての正当性' (legitimacy as a leader). This emphasizes that the legitimacy is tied to a specific role or function. When writing, remember that this is a formal term; in casual speech, Japanese people might use '正しいかどうか' (tashii ka dō ka - whether it's correct or not) instead.

その手続きの正当性を欠いている。(Sono tetsuzuki no seitōsei o kaite iru.) - It lacks the legitimacy of that procedure.

歴史的な正当性を根拠にする。(Rekishiteki na seitōsei o konkyo ni suru.) - To base [something] on historical legitimacy.

You are most likely to encounter 正当性 (seitōsei) in high-level media consumption, specifically news broadcasts, documentaries, and editorials. NHK news frequently uses this word when discussing international conflicts, government policy changes, or court rulings. For example, when a new law is passed that sparks public debate, commentators will analyze the 'procedural legitimacy' (手続き的正当性 - tetsuzukiteki seitōsei) of the legislative process. In the courtroom, lawyers use it to argue why a piece of evidence should be admitted or why a certain action taken by their client was justified under the law. If you are watching a political drama like 'House of Cards' (dubbed or subbed in Japanese), this word will appear constantly as characters vie for power and try to justify their schemes.

Business Meetings: In a corporate setting, it is used during board meetings or strategic planning. A manager might say, 'We need to establish the 正当性 of this project before requesting a budget,' meaning they need a solid justification for why the project is necessary and valid.

民主主義における選挙の正当性。(Minshushugi ni okeru senkyo no seitōsei.) - The legitimacy of elections in a democracy.

Furthermore, you will find it in academic textbooks, particularly those concerning sociology, law, and philosophy. Max Weber's theories on 'legitimate authority' are translated into Japanese using the term '正当的支配' (seitōteki shihai). In these contexts, the word is used to explore why people obey certain rules and how those rules are justified. If you are a student at a Japanese university, you will hear professors use it to challenge students' arguments, asking if their logic has sufficient 正当性. It is a hallmark of critical thinking in Japanese. Even in sports, if a controversial call is made by a referee, sports analysts might discuss the 正当性 of the decision based on the rulebook, though they might use slightly less formal language depending on the program's tone.

データの収集方法に正当性があるか確認する。(Dēta no shūshū hōhō ni seitōsei ga aru ka kakunin suru.) - Confirm whether there is validity in the data collection method.

A frequent mistake learners make is confusing 正当性 (seitōsei) with 正確性 (seikakusei). While they look similar because they both end in '性' and start with '正,' they have very different meanings. Seikakusei means 'accuracy' or 'precision' (e.g., the accuracy of a clock or a calculation), whereas seitōsei means 'legitimacy' or 'justifiability.' If you say a report lacks seitōsei, you are saying it is biased or illegal; if you say it lacks seikakusei, you are saying the numbers are wrong. Another common confusion is with 正直 (shōjiki), which means 'honesty.' Honesty is a personal trait of a human being, while legitimacy is a quality of an action, claim, or system. You cannot say 'a person is 正当性,' but you can say 'a person's actions have 正当性.'

Mistake: Overuse in Casual Settings: Using 正当性 when you just mean 'you're right' in a casual chat. Instead of '君の意見には正当性がある,' just say '君の言う通りだ' (Kimi no iu tōri da).

× この時計の正当性は高い。
○ この時計の正確性は高い。(This clock's accuracy is high.)

Learners also struggle with the difference between 妥当性 (datōsei) and 正当性 (seitōsei). Datōsei means 'validity' in the sense of being appropriate, reasonable, or logically sound for a specific purpose (often used in science and statistics). Seitōsei is more about being 'right' in a moral, legal, or authoritative sense. For example, a method might be datō (appropriate) for an experiment, but the experiment itself might lack seitōsei if it violates ethical laws. Finally, be careful with the particle usage. You don't 'do' 正当性 (正当性する is wrong); it is always a noun that 'exists' (ある) or is 'claimed' (主張する).

× 彼は正当性な人だ。
○ 彼の行為には正当性がある。(His actions have legitimacy.)

When you want to express 'validity' or 'rightness' in Japanese, several words might come to mind, each with its own specific nuance. 合法性 (gōhōsei) is the most direct alternative when you are strictly talking about 'legality.' While seitōsei can include moral and logical rightness, gōhōsei only cares about whether something follows the written law. Another similar word is 妥当性 (datōsei), which we mentioned earlier. This is used when something is 'proper' or 'reasonable' given the circumstances. In scientific research, researchers check the datōsei of their conclusions. If you want to talk about 'fairness' or 'justice,' the word 正義 (seigi) is used, but this is a much broader, more abstract concept than seitōsei.

正当性 vs. 合理性: 合理性 (gōrisei) means 'rationality' or 'efficiency.' A decision can be rational (gōriteki) but not legitimate (seitōteki) if it is illegal or immoral.

正当性 vs. 真実性: 真実性 (shinjitsusei) refers to 'truthfulness' or 'authenticity.' This is used to describe whether a document or a story is actually true.

その主張の妥当性を検証する。(Sono shuchō no datōsei o kenshō suru.) - Verify the validity/reasonableness of that claim.

In more casual or semi-formal settings, you might use 正当な (seitō na), the adjective form. For example, '正当な理由' (seitō na riyū) means 'a valid reason' or 'a justifiable reason.' If you miss work, your boss will ask for a seitō na riyū. If you want to say something is 'correct' in a general sense, 正しい (tadashii) is your best bet. If you want to say something is 'legal,' 法律にかなった (hōritsu ni kanatta) is a common phrase. Choosing the right word depends on whether you are emphasizing the law (gōhōsei), logic (datōsei), efficiency (gōrisei), or the overall rightful authority (seitōsei).

それは正当性というより、単なる効率性の問題だ。(Sore wa seitōsei to iu yori, tannaru kōrisei no mondai da.) - That is less a matter of legitimacy and more a matter of simple efficiency.

How Formal Is It?

Fun Fact

The character '当' (tō) originally depicted a field (田) being divided equally, which eventually evolved to mean 'appropriate' or 'fitting.'

Pronunciation Guide

UK /seɪ.toʊ.seɪ/

US /seɪ.toʊ.seɪ/

Japanese is a pitch-accent language. In 'Seitōsei', the pitch usually starts low on 'Se', rises on 'i-tō', and stays relatively flat or drops slightly on 'sei'.

Rhymes With

Keitōsei (Systematicity) Meitōsei (Clarity - rare) Teitōsei (Mortgageability - very rare) Seitō (Political party) Meitō (Famous sword) Reitō (Freezing) Keitō (System) Seitō (Orthodoxy)

Common Errors

Pronouncing 'tō' too short (it must be a long vowel).
Confusing the pitch with 'Seitō' (political party), which has a different accent pattern.
Mispronouncing 'sei' as 'sigh'.
Failing to sustain the long vowels, making it sound like 'setose'.

Difficulty Rating

Reading 4/5

Requires knowledge of N2/N1 level kanji and formal vocabulary.

Writing 4/5

Using it correctly requires understanding abstract noun structures and formal particles.

Speaking 5/5

Rarely used in daily speech; requires a high level of context awareness to not sound overly stiff.

Listening 4/5

Common in news and documentaries, but requires distinguishing from similar-sounding words.

What to Learn Next

Prerequisites

正しい (tadashii) 理由 (riyū) 法律 (hōritsu) 権利 (kenri) 認める (mitomeru)

Learn Next

妥当性 (datōsei) 合法性 (gōhōsei) 合理性 (gōrisei) 正義 (seigi) 倫理 (rinri)

Advanced

正統性 (seitōsei - orthodoxy) 適法性 (tekihōsei) 実証主義 (jisshōshugi) 主権 (shuken)

Grammar to Know

Abstract Noun Suffix 〜性 (-ity/-ness)

正確性 (accuracy), 可能性 (possibility), 正当性 (legitimacy).

Noun + としての (As a...)

リーダーとしての正当性 (Legitimacy as a leader).

Verb + ことを目的とする (Aiming to...)

正当性を証明することを目的とする (Aiming to prove legitimacy).

Passive with 'Towarete iru' (Is being questioned)

正当性が問われている (Legitimacy is being questioned).

Noun + を欠く (To lack...)

正当性を欠く (To lack legitimacy).

Examples by Level

これは正しいですか？

Is this correct?

Uses the adjective 'tadashii', the root concept of 'seitōsei'.

ルールを守りましょう。

Let's follow the rules.

Focuses on the concept of 'rules' which is central to legitimacy.

いい理由がありますか？

Do you have a good reason?

Simple way to ask for justification.

それはだめです。

That is not allowed.

Expressing lack of 'seitōsei' in the simplest terms.

正しい答えは何ですか？

What is the correct answer?

Using 'tadashii' for factual correctness.

みんなで決めました。

We decided together.

The basis of democratic legitimacy (agreement).

それは公平ですか？

Is that fair?

Fairness (kōhei) is a component of legitimacy.

本に書いてあります。

It is written in the book.

Authority from a written source.

正当な理由を教えてください。

Please tell me a valid reason.

Uses 'seitō na' (adjective) + 'riyū' (reason).

このルールの正当性を考えます。

I will think about the validity of this rule.

Introduction of the noun 'seitōsei'.

彼は正当な権利を持っています。

He has a legitimate right.

Uses 'seitō na' with 'kenri' (right).

そのやり方は正当ではありません。

That method is not legitimate.

Negative form: 'seitō dewa arimasen'.

裁判で正当性を証明します。

I will prove the legitimacy in court.

Formal context: 'seitōsei o shōmei suru'.

正当な評価が必要です。

A fair/legitimate evaluation is necessary.

Using 'seitō na' for fairness in judgment.

彼女は正当に怒っています。

She is rightfully angry.

Adverbial use: 'seitō ni' (rightfully).

この契約には正当性がありますか？

Is there legitimacy in this contract?

Questioning existence using 'ga arimasu ka'.

政府の正当性が問われている。

The legitimacy of the government is being questioned.

Passive form: 'seitōsei ga towarete iru'.

その主張には一定の正当性がある。

There is a certain level of validity to that claim.

'Ittei no' (a certain level of) qualifies the degree.

自分の行為の正当性を主張した。

He asserted the legitimacy of his own actions.

'Seitōsei o shuchō suru' is a common B1-B2 phrase.

データの正当性を確認してください。

Please confirm the validity of the data.

Context: Research and verification.

歴史的な正当性を根拠にしている。

It is based on historical legitimacy.

'Konkyo ni shite iru' (is based on).

その手続きは正当性を欠いている。

That procedure lacks legitimacy.

'Seitōsei o kaku' (to lack legitimacy).

民主主義における正当性の源泉は何ですか？

What is the source of legitimacy in a democracy?

'Gensen' (source) is a sophisticated pairing.

彼はリーダーとしての正当性を失った。

He lost his legitimacy as a leader.

'Toshite no' (as a) defines the role.

武力行使の正当性を国際社会に訴える。

To appeal the legitimacy of the use of force to the international community.

Focuses on geopolitical legitimacy.

新政権は国民からの正当性を得ようとしている。

The new administration is trying to gain legitimacy from the citizens.

'Seitōsei o eru' (to gain legitimacy).

その判決の正当性について議論が分かれている。

Discussions are divided regarding the legitimacy of that verdict.

'Giron ga wakarete iru' (opinions are divided).

正当性を担保するための法整備が必要だ。

Legal frameworks are necessary to guarantee legitimacy.

'Tanpo suru' (to guarantee/secure) is high-level.

彼の解雇には正当性がないと判断された。

It was judged that there was no legitimacy in his dismissal.

Legal judgment context.

手続き的正当性が守られていない。

Procedural legitimacy is not being upheld.

'Tetsuzukiteki' (procedural) is a specific type of legitimacy.

伝統的な正当性を重んじる文化だ。

It is a culture that values traditional legitimacy.

'Omonjiru' (to value/respect).

情報の正当性を裏付ける証拠が見当たらない。

No evidence can be found to support the validity of the information.

'Urazukeru' (to support/corroborate).

支配の正当性が崩壊し、革命が起きた。

The legitimacy of the rule collapsed, and a revolution occurred.

Political science context: 'Seitōsei no hōkai'.

マックス・ウェーバーは正当的支配の三類型を提示した。

Max Weber presented three types of legitimate rule.

Academic reference to sociological theory.

その組織は、自らの正当性を自己定義しているに過ぎない。

That organization is merely self-defining its own legitimacy.

'Jiko teigi' (self-definition) implies a critique.

グローバル・ガバナンスにおける正当性の欠如が問題だ。

The lack of legitimacy in global governance is an issue.

Complex abstract subject: 'Global governance'.

正当性をめぐる言説の変遷を辿る。

To trace the transition of discourse surrounding legitimacy.

'Gensetsu' (discourse) and 'hensen' (transition).

法の正当性は、その道徳的基盤に依存する。

The legitimacy of law depends on its moral foundation.

'Izon suru' (to depend on).

カリスマ的正当性は、指導者の資質に由来する。

Charismatic legitimacy stems from the leader's qualities.

'Karisuma-teki' (charismatic) + 'yurai suru' (stems from).

正当性の再構築には、透明性の向上が不可欠だ。

Improving transparency is essential for the reconstruction of legitimacy.

'Saikōchiku' (reconstruction) and 'fukatsu' (essential).

正当性の概念は、主権国家体制の変容とともに進化した。

The concept of legitimacy evolved along with the transformation of the sovereign state system.

Extremely formal academic tone.

討議民主主義は、合意形成プロセスに正当性の根拠を求める。

Deliberative democracy seeks the grounds for legitimacy in the consensus-building process.

'Tōgi minshushugi' (deliberative democracy).

ポスト真実の時代において、科学的正当性は揺らいでいる。

In the post-truth era, scientific legitimacy is wavering.

'Post-truth' (posuto-shinjitsu) context.

実証法学は、法の正当性をメタ物理的な根拠から切り離した。

Legal positivism detached the legitimacy of law from metaphysical grounds.

Philosophical terminology: 'Jisshō hōgaku' (legal positivism).

国家の正当性は、単なる暴力の独占ではなく、承認に依拠する。

State legitimacy relies on recognition, not merely the monopoly on violence.

'Ikyo suru' (to rely/depend on).

正当性の簒奪は、長期的には体制の不安定化を招く。

The usurpation of legitimacy leads to the destabilization of the regime in the long run.

'Sandatsu' (usurpation) is a very rare C2 word.

文化的多元主義は、普遍的な正当性の基準に疑問を投げかける。

Cultural pluralism casts doubt on universal standards of legitimacy.

'Gimon o nagekakeru' (to cast doubt).

正当性の言説空間を分析し、権力構造を解明する。

To analyze the discursive space of legitimacy and elucidate the power structure.

'Gensetsu kūkan' (discursive space) and 'kaimei' (elucidation).

Synonyms

妥当性合法性適法性正しさ

Antonyms

不当性違法性

Common Collocations

正当性を主張する

正当性を疑う

正当性を欠く

正当性を証明する

正当性を担保する

歴史的正当性

手続き的正当性

正当性を問う

正当性が認められる

正当性の危機

Common Phrases

正当な理由

— A valid or justifiable reason for doing something.

正当な理由があれば、遅刻も認められます。

正当な評価

— A fair and accurate assessment of someone's work or value.

社員に正当な評価を与えるべきだ。

正当な権利

— A legitimate right that one is entitled to hold.

それは彼の正当な権利だ。

正当防衛

— Self-defense; a legal justification for using force.

彼の行為は正当防衛と見なされた。

正当な手続き

— Due process; following the correct legal steps.

正当な手続きを踏んで解雇する。

正当な報酬

— A fair and legitimate payment for services rendered.

働いた分、正当な報酬を受け取る。

正当な手段

— Legitimate means or methods to achieve a goal.

正当な手段で勝負したい。

正当な後継者

— A legitimate successor or heir.

彼こそが正当な後継者だ。

正当な要求

— A justifiable or valid demand.

組合は正当な要求を突きつけた。

正当な批判

— Legitimate or constructive criticism.

それは正当な批判として受け止める。

Often Confused With

正当性 vs 正確性 (seikakusei)

Means 'accuracy.' Don't use it when you mean 'legitimacy.'

正当性 vs 正直 (shōjiki)

Means 'honesty' (a personality trait). 'Seitōsei' is a conceptual quality.

正当性 vs 正当 (seitō)

The adjective form. 'Seitōsei' is the noun form.

Idioms & Expressions

"正鵠を射る"

— To hit the mark; to be exactly right or relevant. Related to the 'tō' in seitō.

彼の指摘は正鵠を射ている。

Formal/Literary

"錦の御旗を掲げる"

— To use a prestigious cause to justify one's actions (like a 'banner of legitimacy').

改革という錦の御旗を掲げて増税する。

Literary/Political

"大義名分"

— A noble cause or a legitimate reason that justifies an action.

戦争を始めるための大義名分が必要だ。

Formal

"理にかなう"

— To make sense; to be reasonable or logical.

彼の説明は理にかなっている。

Neutral

"非の打ち所がない"

— Impeccable; beyond reproach; perfectly legitimate/correct.

彼の論理は非の打ち所がない。

Neutral

"筋を通す"

— To act with integrity; to ensure one's actions are logically and morally consistent.

辞める前に、きちんとした筋を通すべきだ。

Neutral

"折り紙付き"

— Guaranteed; certified as authentic or legitimate.

彼の技術は折り紙付きだ。

Idiomatic

"お墨付きをもらう"

— To receive an official seal of approval or legitimacy from an authority.

政府からお墨付きをもらったプロジェクトだ。

Idiomatic

"名実ともに"

— In both name and reality; truly legitimate in every sense.

彼は名実ともに世界のトップだ。

Neutral

"後ろ指を指されない"

— To act so legitimately that no one can criticize you behind your back.

後ろ指を指されないような生き方をしたい。

Idiomatic

Easily Confused

正当性 vs 妥当性 (datōsei)

Both translate to 'validity' in English.

Datōsei is about logical appropriateness or scientific validity; Seitōsei is about legal or moral legitimacy/authority.

この計算式の妥当性は高いが、その目的の正当性には疑問がある。

正当性 vs 合法性 (gōhōsei)

Both deal with being 'right' under rules.

Gōhōsei is strictly about the written law; Seitōsei can include moral rightness and social acceptance.

その行為は合法性はあるが、倫理的な正当性に欠ける。

正当性 vs 正統性 (seitōsei)

They sound exactly the same (homophones).

正当性 is 'justifiability'; 正統性 is 'orthodoxy' or 'traditional lineage.'

彼は正統な後継者だが、その行動に正当性はない。

正当性 vs 合理性 (gōrisei)

Both are abstract qualities used in formal debate.

Gōrisei is about logic and efficiency; Seitōsei is about rightfulness and authority.

経済的な合理性だけで正当性を判断してはならない。

正当性 vs 真実性 (shinjitsusei)

Both relate to whether something 'holds up.'

Shinjitsusei is about whether something is true or a lie; Seitōsei is about whether it is justified.

情報の真実性と、それを公開する正当性を検討する。

Sentence Patterns

[Noun]の正当性を疑う

彼はその手続きの正当性を疑った。

[Noun]には正当性がある

この主張には十分な正当性がある。

[Noun]としての正当性を失う

王は指導者としての正当性を失った。

正当性を担保するために[Action]

正当性を担保するために、第三者機関が調査を行う。

正当性をめぐる[Noun]

正当性をめぐる議論が続いている。

[Noun]の正当性を欠いている

その法律は民主的な正当性を欠いている。

正当性の根拠を[Noun]に求める

彼は権力の正当性の根拠を神話に求めた。

正当性の再構築を図る

政府は信頼回復と正当性の再構築を図っている。

Word Family

Nouns

正当 (Legitimacy/Justness)

正当化 (Justification)

不正 (Injustice/Illegality)

Verbs

正当化する (To justify)

正当づける (To give grounds for)

Adjectives

正当な (Legitimate/Valid)

不正な (Unfair/Illegal)

正義 (Justice)

妥当 (Appropriate)

合法 (Legal)

正確 (Accurate)

適正 (Proper)

How to Use It

frequency

Common in media and formal writing, rare in daily life.

Common Mistakes

Using 正当性 for 'accuracy' of a clock. → 正確性 (seikakusei)
Accuracy of physical measurements uses 'seikakusei'. 'Seitōsei' is for moral/legal validity.
Saying '彼は正当性な人だ' (He is a legitimate person). → 彼は正当な人だ (He is a just person) or 彼の行為には正当性がある。
'Seitōsei' is an abstract noun, not a personality trait. Use the 'na-adjective' or the 'ga aru' structure.
Confusing '正当性' with '正直' (honesty). → 正直 (shōjiki)
If someone tells the truth, they are 'shōjiki.' If their actions are legally justified, they have 'seitōsei.'
Using '正当性する' as a verb. → 正当化する (seitōka suru)
To 'justify' something requires the '-ka suru' suffix, which means 'to make into.'
Misspelling 'tō' as '統' in a legal context. → 正当性 (seitōsei)
Using '統' refers to lineage or orthodoxy, which is a different concept than legal justifiability.

Tips

Use with 'Utagau'

Whenever you see a news report about a controversial election, look for the phrase '正当性を疑う' (utagau - to doubt). It is the most common way to express skepticism about authority.

Check the Middle Kanji

Make sure to use '当' (to hit/appropriate). If you use '統' (to rule/lineage), you are talking about 'orthodoxy,' which is a different concept used for royal bloodlines or religious traditions.

The 'Ga Aru' Pattern

The simplest way to use the word is '[Noun] + には正当性がある'. For example: '彼の怒りには正当性がある' (His anger is justified).

Justification vs Legitimacy

While English often uses 'justification,' Japanese uses '正当化' (seitōka) for the act of justifying and '正当性' (seitōsei) for the state of being legitimate.

Sounding Smart

Using '正当性' in a business context when discussing company policy or legal compliance will instantly make your Japanese sound more professional and high-level.

News Keywords

Listen for 'Seitōsei' during the first 5 minutes of NHK News 7; it often appears when world leaders meet or when new laws are introduced.

Avoid 'Tadashisa'

While 'tadashisa' (correctness) exists, it sounds a bit childish in a formal essay. Replace it with '正当性' or '妥当性' for a better grade.

The 'Receipt' Analogy

Think of 'Seitōsei' as the receipt of an action. It's the proof that you had the right to do it.

Global Issues

Use this word when writing about international law or human rights; it is the standard term used in translations of UN documents.

Pitch Accent

Remember the pitch rises on the 'i' of 'sei' and stays high through 'tō'. This distinguishes it from 'seitō' (political party).

Memorize It

Mnemonic

Imagine a judge hitting a 'TŌ' (target) with a 'SEI' (straight/correct) arrow to prove his 'SEI' (quality/nature). SEI-TŌ-SEI.

Visual Association

Visualize a golden seal of approval placed on a law book. The seal represents the 'quality' (性) of being 'correct' (正) and 'appropriate' (当).

Word Web

Law Government Rules Justification Validity Fairness Authority Proof

Challenge

Try to find one news article today in Japanese (e.g., on NHK News) that uses the word '正当性' and identify who is claiming it.

Word Origin

The word is composed of Sinitic (Chinese-derived) characters. '正' (sei/shō) dates back to ancient oracle bone script, depicting a foot moving towards a city, implying a 'straight' or 'correct' path.

Original meaning: Originally, '正当' meant 'to be appropriate' or 'to hit the target exactly.'

Sino-Japanese (Kango).

Cultural Context

Be careful when using this word regarding sensitive historical or territorial disputes, as 'seitōsei' is a highly charged word in these contexts.

In English, 'legitimacy' is often used in political science, while 'validity' is used in logic and science. 'Seitōsei' covers both.

Max Weber's 'Politics as a Vocation' (translated as 'Shokugyō to shite no seiji') The Japanese Constitution (Nihonkoku Kenpō) The concept of 'Mandate of Heaven' in East Asian history

Practice in Real Life

Real-World Contexts

Politics

政府の正当性
選挙の正当性
支配の正当性
正当性の危機

Law

正当な手続き
正当防衛
正当性を証明する
不当な判決

Business

プロジェクトの正当性
解雇の正当性
正当な評価
正当な報酬

Academic Research

データの正当性
論理の正当性
正当性を検証する
方法論の正当性

History

歴史的正当性
王位継承の正当性
領土の正当性
正当な後継者

Conversation Starters

"その新しいルールの正当性について、どう思いますか？ (What do you think about the legitimacy of that new rule?)"

"このデータの正当性を証明するには、何が必要でしょうか？ (What is needed to prove the validity of this data?)"

"リーダーとしての正当性を保つためには、何が最も重要だと思いますか？ (What do you think is most important to maintain legitimacy as a leader?)"

"歴史的な正当性は、現代の政治にどの程度影響を与えるべきでしょうか？ (To what extent should historical legitimacy influence modern politics?)"

"そのプロジェクトには、予算を請求するだけの正当性がありますか？ (Does that project have enough legitimacy to request a budget?)"

Journal Prompts

自分が正しいと信じていることの正当性を、客観的な理由を挙げて説明してください。 (Explain the legitimacy of something you believe is right, giving objective reasons.)

社会における『正当性』と『合法性』の違いについて、自分の考えを書いてください。 (Write your thoughts on the difference between 'legitimacy' and 'legality' in society.)

過去に、自分の正当性を主張しなければならなかった時の経験を記述してください。 (Describe an experience from the past when you had to assert your own legitimacy.)

インターネット上の情報の正当性を判断するために、どのような基準を使っていますか？ (What criteria do you use to judge the validity of information on the internet?)

もし自分が新しい国のリーダーになったら、どのようにして国民からの正当性を得ますか？ (If you became the leader of a new country, how would you gain legitimacy from the citizens?)

Frequently Asked Questions

10 questions

No, for a test answer, use '正確' (seikaku) or '正解' (seikai). '正当性' is for legitimacy and justification, not factual correctness.

No, it is very formal. In daily life, you would say '正しい理由' (tadashii riyū) or 'ちゃんとした理由' (chan to shita riyū).

'正当' is an adjective (na-adjective) meaning 'legitimate.' '正当性' is the noun meaning 'legitimacy.' You say '正当な理由' but '理由の正当性'.

It is '正当防衛' (seitō bōei). It uses the same 'seitō' root, meaning a 'justifiable' defense.

Usually, scientists use '妥当性' (datōsei) to mean 'validity' of a method. '正当性' would only be used if discussing the ethics or the right to conduct the experiment.

It is '手続き的正当性' (tetsuzukiteki seitōsei). This is a common phrase in law and politics.

It is a neutral concept, but 'having it' is usually seen as positive for the person claiming it. However, it can be used to question or deny someone's authority.

No. You must say '正当化する' (seitōka-suru) which means 'to justify'.

Yes, '正義' (seigi) is justice, and '正当性' is the quality of being in line with that justice or law.

It is a suffix that sounds like 'say'. It is used in many abstract nouns like 'kanōsei' (possibility).