Composed of 下 ('lower, below') + 唇 ('lip'). The kanji 下 causes the second element to undergo rendaku (sequential voicing): くちびる becomes ぐちびる in some compounds — but not here. The reading is したくちびる, with no voicing on the くち part, although したくちびる and したぐちびる are both encountered; したくちびる is the standard form recorded in major dictionaries.
USAGE:
As with most paired body parts, 下唇 is used mainly when the distinction between upper and lower matters: in beauty/cosmetic instructions, dental and medical contexts, and in describing facial expressions. In ordinary speech where the distinction is unimportant, Japanese speakers say 唇 ('lips') without specifying.
COMMON COLLOCATIONS:
- 下唇を噛む: to bite one's lower lip (a common gesture of frustration, hesitation, or held-back emotion)
- 下唇を突き出す: to push out one's lower lip (a sulky/pouting gesture)
- 下唇を舐める: to lick one's lower lip
- 下唇が震える: for one's lower lip to tremble (a sign of crying or strong emotion)
- 下唇が切れる: for one's lower lip to be cut/split
- 下唇が荒れる: for one's lower lip to become chapped
- 下唇にリップを塗る: to apply lip balm to the lower lip
SIMILAR WORDS:
- 唇: lip, lips — the general word; preferred in everyday speech.
- 上唇: upper lip — the paired counterpart.
- 口: mouth — much broader; the whole opening, not just the lips.
- 口元: area around the mouth — the broader region surrounding the mouth, including the surrounding skin.
CULTURAL NOTE:
In Japanese fiction and manga, biting the lower lip (下唇を噛む) is a stock visual cue for a character holding back tears, hiding frustration, or steeling themselves for an unwanted task. The expression is common enough that readers immediately recognize the implied emotional state.