How to say "mouth" in Japanese

• 口くちJLPT N5approx.Common
  nounThe ordinary word for the mouth as a body part, of people and animals, used for eating and speaking. This is the default choice whenever you mean the organ itself.
  椅子いすに横よこたわる私に、歯科衛生士しかえいせいしの女性じょせいが「はい、お口くちを開あけてください」と言いったのです。↗

  The woman dental hygienist said to me, lying down in the chair, "Right, please open your mouth."
• 口腔こうこうCommon
  nounThe anatomical term for the oral cavity — the mouth as a bodily structure or interior space. You meet it in medical, dental, and scientific writing rather than in everyday conversation.
• 入り口いりぐちJLPT N5approx.Common
  nounFor 'mouth' in the sense of an opening or way in — an entrance, gate, or approach, as in the mouth of a cave. It never means the mouth as a body part.
  １台だいの車くるまが入り口いりぐちに止とまった。↗

  A car stopped at the entrance.
• 口先くちさきCommon
  nounPoints to the lips and the front of the mouth; for animals, the snout or proboscis. Not the ordinary word for the mouth as a whole — use 口 for that.
  言葉ことばが口先くちさきまで出でかかっているのだが、自分じぶんのいいたいことをどう表現ひょうげんしたらいいのかよくわからない。↗

  The words are on the tip of my tongue, but I don't quite know how to put what I want to say.

Use 口 for the mouth as a body part, 口腔 for the anatomical oral cavity in medical contexts, 「入り口」 when English 'mouth' means an entrance or opening, and 口先 for the lips or an animal's snout.

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

• 口くちmouth
• 口腔こうこうoral cavity
• 入り口いりぐちentrance
• 口くmouth
• マウスmouth
• 口元くちもとmouth
• 口付きくちつき(in the shape of a) mouth
• 口先くちさきlips
• 落ち口おちぐちmouth (of a sewer, etc.)
• 鼻の下はなのしたmouth
• 口吻こうふんlips