How to say "complement" in Japanese

• 補足ほそくJLPT N1approx.Common
  no-adjective, suru verb, transitive verbCovers the sense of complementing as supplementing — adding something to make an explanation or account more complete. This is the usual choice when you mean 'to complement' in the sense of filling a gap.
  彼かれの説明せつめいに何なんか補足ほそくすることがありますか。↗

  Do you have anything to add to his explanation?
• 定員ていいんJLPT N2approx.Common
  nounCovers the full complement of people, such as a prescribed or fixed number of students or staff. As a verb sense of 'to complement', this is not the word you want; it really means a numerical limit or quota.
• 友ともJLPT N3approx.Common
  nounCovers complement in the figurative sense of a companion or accompaniment — something that pairs well with another, such as a book being a fine complement to a journey. A somewhat literary way to express the idea.

Use 補足 for a complement that supplements or fills out something, 定員 for a full complement as a prescribed number of people, and 友 for a complement in the sense of a companion or accompaniment.

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

• 補足ほそくsupplement
• 定員ていいんfixed number (of people)
• 足したしsupplement
• 補い合うおぎないあうto complement
• 補数ほすうcomplement (of a number)
• 補語ほごcomplement
• 相補そうほcomplement
• 補体ほたいcomplement (blood proteins)
• 有無相通じるうむあいつうじるto help each other
• 補集合ほしゅうごうcomplementary set
• 付かたりつかたりaddition
• 友ともaccompaniment
• 余数よすうcomplement (of a number)