任意(にんい)

にんい
noun, no-adjective
optional; voluntary; arbitrary
1. optional; voluntary
Left to one's own choice or discretion; not compulsory. Commonly seen on forms, in instructions, and in legal contexts.
この項目(こうもく)は任意(にんい)です。
This field is optional.
任意(にんい)の保険(ほけん)に加入(かにゅう)するかどうかは本人(ほんにん)が決(き)めることだ。
Whether to enroll in optional insurance is for the individual to decide.
警察(けいさつ)が任意(にんい)で事情聴取(じじょうちょうしゅ)を行(おこな)った。
The police conducted a voluntary interview.
2. arbitrary; any (in mathematics or logic)
Chosen without specific criteria; any value or element that satisfies certain conditions. Used in technical and academic contexts.
任意(にんい)の正(せい)の整数(せいすう)nについて成(な)り立(た)つ。
This holds for any positive integer n.
任意(にんい)の点(てん)Pを選(えら)び、そこから直線(ちょくせん)を引(ひ)く。
Choose an arbitrary point P and draw a line from it.
この定理(ていり)は任意(にんい)の三角形(さんかくけい)に適用(てきよう)できる。
This theorem can be applied to any triangle.

USAGE:
任意(にんい) is used as a no-adjective (任意(にんい)の) or as a noun. In everyday Japanese, it most often means "optional" or "voluntary." In police and legal contexts, 任意(にんい) contrasts with 強制(きょうせい) (compulsory).

COMMON COLLOCATIONS:

  • 任意(にんい)加入(かにゅう) (voluntary enrollment)
  • 任意(にんい)保険(ほけん) (optional insurance)
  • 任意(にんい)同行(どうこう) (voluntary accompaniment to police station)
  • 任意(にんい)の値(あたい) (any value)

NUANCE:
In police terminology, 任意(にんい) (voluntary questioning/accompaniment) contrasts with 逮捕(たいほ) (arrest). While technically voluntary, 任意(にんい)同行(どうこう) in practice is difficult to refuse.

Related Words

Antonym: 強制的(きょうせいてき) (compulsory)
general
Added 2026.3.9 17:40 · Revised 2026.4.18 0:06
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