乳房|ちぶさchibusa[1]atamadaka (head-high)

1. nounbreast; udder
   乳房ちぶさにしこりがあります。↗

   I have a lump in my breast.

• SynonymバストNeutralLoanword for the bust measurement, used above all as a clothing-size term, as in 「バストサイズ」.
• SynonymおっぱいCasualColloquial, childlike word for breasts or breast milk; affectionate but can sound vulgar. Children use it, and adults in casual speech.
• Synonym胸むねNeutralBroader word for the chest, also covering the heart and feelings; serves as the everyday, polite euphemism for the breasts.
• Related乳ちちNeutralNative word for milk or the breast; used mainly in nursing contexts such as 「乳を飲ませる」. Less clinical than 「乳房」.

「乳房」 is the formal word; read ちぶさ it sounds literary, and in medical terms like 「乳房検診」 it is read にゅうぼう. In everyday speech 「胸」 is the polite choice and 「おっぱい」 the colloquial one; use 「バスト」 for clothing sizes and 「乳」 for nursing.

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

1. 哺乳類ほにゅうるいのメスが具そなえる外性がいせい器きの一ひとつ。女性じょせいでは乳腺にゅうせんから乳汁にゅうじゅうを分泌ぶんぴつし、哺乳ほにゅう器きとしての機能きのうを内包ないほうする。