性|せいsei[1]atamadaka (head-high)

1. nounnature (of a person)
   習ならい性せいとなる。↗

   Habit is second nature.
2. nounsex; gender
3. nounsex (i.e. sexual attraction, activity, etc.)
   最近さいきんの漫画まんがは暴力ぼうりょくや性せいの描写びょうしゃが多おおすぎる。↗

   Recent comics have too many violent and sexual scenes.
4. noun, grammargender
5. noun (suffix)-ty; -ity; -ness; -cyindicating quality or condition
   ３番目ばんめに考慮こうりょすべき事柄ことがらは、カーペットの時代じだい性せいである。↗

   The age of the carpet is a third thing to consider.

• Synonym性格せいかくNeutralThe everyday word for a person's character, as in 「明るい性格」; the most common choice in daily use. 「性」 alone usually means sex or innate nature.
• Synonym性質せいしつWrittenWritten/formal prose for the properties or characteristics of things, as in 「水の性質」; applies to people as well as objects.
• Synonym気質きしつWrittenWritten/formal prose for temperament or disposition, of individuals or groups, as in 「穏やかな気質」. Read 「かたぎ」, it refers to the shared ways of a type of person.
• Synonym性根しょうねCasualColloquial, with a scolding tone: one's inner character or backbone, as in 「性根を入れ替える」.
• Synonym人柄ひとがらNeutralA person's character as others see them — the impression they give, as in 「人柄がいい」.
• Synonym人格じんかくWrittenWritten/formal prose for personality or moral character, as in 「人格者」; stresses moral standing.
• Synonym天性てんせいNeutralInnate disposition or talent, as in 「天性の明るさ」; can carry praise or criticism.
• Synonym本性ほんしょうNeutralOne's true nature, as in 「本性を現す」; often negative. To say someone shows their true self, use this, not 「性」.
• Synonym性分しょうぶんWrittenWritten/formal prose for one's inborn temperament, as in 「損な性分」; often with a resigned nuance.
• Synonym根性こんじょうCasualColloquial for grit and determination, or a bad streak in one's nature, as in 「根性がある」.
• Synonym禀性ひんせいWrittenWritten/formal prose for one's inborn nature; not much used. Stresses what one is born with.
• SynonymきっぷCasualTemper or spirit, especially one shared by the people of a group or region. 「気っぷがいい」 often describes someone straightforward and generous.
• Synonym気稟きひんWrittenWritten/formal prose for innate temperament; very rare. Say 「性格」 or 「気質」 in daily life.
• Related品性ひんせいWrittenWritten/formal prose for moral character, as in 「品性下劣」; the moral side is what counts.
• Related質しつNeutralQuality or calibre, as in 「質が高い」; the focus is on how good or bad something is.
• Related素質そしつNeutralNatural aptitude or makings, as in 「音楽の素質」; stresses latent ability.
• RelatedネイチャーNeutralLoanword for nature — the natural world or innate nature; mostly seen in magazine titles, rare in daily use.
• RelatedキャラクターCasualColloquial loanword for personality or (fictional) character, as in 「キャラが濃い」.
• Related人となりひととなりWrittenWritten/formal prose for what a person is like — their makeup and disposition, as in 「彼の人となり」.
• Related性情せいじょうWrittenWritten/formal prose for disposition and state of heart; not much used, covering both character and feelings.

Use 「性」 for sex, gender and sexual matters; it can also mean innate nature, as in 「人の性」. For personality pick 「性格」; for character as others see it, 「人柄」; for the properties of things, 「性質」; for natural talent, 「素質」; for one's true self, 「本性」; for grit, 「根性」. Most others are rarer or register-marked: written 「気質」「性分」「性情」 for temperament, 「天性」「禀性」 for what is inborn, colloquial 「性根」「気っ風」 for character with a judgemental or folksy ring.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. （セイ）生物せいぶつ的てきな男女だんじょ又または雌雄しゆうの区別くべつ。
2. （セイ）性欲せいよくや性せい衝動しょうどうに関かんすること。
3. （セイ）印欧語いんおうごやセム語派ごはに代表的だいひょうてきにみられる、名詞めいしなどの変化へんかの形態けいたいによって区別くべつされるグループ。おもに、男性だんせい、女性じょせい、中性ちゅうせい、通性つうせいなどに分わけられる。同一どういつ言語げんご内ないでその区分くぶんが多おおい場合ばあいは、名詞めいしクラスと呼よばれる。
4. （ショウ、さが）うまれもって、その人ひとが有ゆうする考え方かんがえかたなどの傾向けいこう。本能ほんのう。
5. （セイ）性質せいしつ、傾向けいこう、性能せいのう、起因きいんするもの、同等どうとう物ものと言いう意味いみの語ごを作つくる。
6. （セイ）性欲せいよく、性せい衝動しょうどう又または性行為せいこういなど、いわゆる性的せいてきな事項じこうに関かんする語ごを作つくる。