breast、bosom与chest这些名词均含“胸、胸部”之意。

breast : 指人或动物的胸部或胸部的前面，也指男人或女人的乳房。

When a woman becomes pregnant her breasts tend to grow larger.

女性怀孕后，乳房会增大。

breast cancer

乳腺癌

bosom : 文学用词，与breast同义，特指女性的乳房，也可用作比喻。

a large/ample bosom

大／丰满的乳房

She held him tightly to her bosom.

她把他紧紧地拥在胸前。

A dark jealousy stirred in his bosom.

他内心生出一阵恶毒的嫉妒。

chest : 指胸膛，即肋骨所包围的部分。

He was shot in the chest at point blank range.

他被近距离射中胸部。

He folded his arms across his chest.

他双臂交叉抱在胸前。