How to say "twins" in Japanese

Choosing the right word

双子ふたごJLPT N3approx.Common
nounCovers both senses of 'twins': the pair of children and a single twin. The word to reach for when talking about family — saying that someone is a twin, or that someone has twins.
その双子ふたごは全まったくよく似にている。↗
The twins are very much alike.
双生児そうせいじCommon
nounAlso means twins, referring to the pair of children born together; in that use it overlaps with 双子, but for one twin alone use 双子. Typical when introducing or describing a pair of twins.
肉体にくたいと精神せいしんとは双生児そうせいじであり、神かみのみがどちらがどちらなのかを知しっている。↗
Body and spirit are twins: God only knows which is which.

双子 covers both senses of 'twins' — the pair and a single twin — while 双生児 is a synonym for the pair, so either works there, but a single twin calls for 双子.

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

Japanese equivalents

双子ふたごtwins
双生児そうせいじtwins
双児そうじtwins
双生そうせいbearing twins

JLPT vocabulary levels are community estimates, not official (no official lists have been published since the 2010 revision).

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