Translation guide
The small projection on the breast. In Japanese, the word differs for humans vs. animals, and for the anatomical part vs. the part of a baby bottle.
The small projection on a human breast.
The most common and neutral word for a human nipple. Used in everyday conversation and medical contexts.
赤ちゃんが乳首を吸っている。
The baby is sucking on the nipple.
A more formal, anatomical term for nipple. Often used in medical or technical contexts.
乳頭の形には個人差があります。
There are individual differences in nipple shape.
The nipple of an animal, especially livestock.
Can be used for animals as well, though it may sound slightly anthropomorphic. Commonly used for pets.
犬の乳首の数は犬によって違います。
The number of nipples varies from dog to dog.
Refers to the udder or teat of livestock, especially cows. Often used in agricultural contexts.
The rubber or silicone part of a baby bottle that the baby sucks on.
Also used for the artificial nipple of a baby bottle. Context makes the meaning clear.
哺乳瓶の乳首を消毒してください。
Please sterilize the nipple of the baby bottle.
The word 乳 (ちち) can mean 'milk' or 'breasts' in general, but not specifically 'nipple'. Use 乳首 (ちくび) for nipple.
Disinfect the cow's teats.