The opposite of fat is thin. Some alternative words are slim, slender, skinny, lean, wiry, petite, and lanky. In general, thin, slim, and slender are more positive, whereas skinny is often used as a criticism or negative point.
胖的反義詞就是thin（瘦）啦。其他的一些表達(dá)包括slim、slender、skinny、lean、wiry、petite和lanky。一般說(shuō)來(lái)，thin、slim和slender是更具褒義的，skinny則是有一點(diǎn)批評(píng)的意味或者貶低的含義。

The words lean and wiry mean that the person is thin AND muscular. The word petite is only used for women, and means that the woman is short AND thin. Finally, the word lanky means tall and thin.
Lean和wiry意味著一個(gè)人不僅很苗條而且有肌肉。Petite則是用來(lái)描述瘦小的女性的。最后，又高又瘦的女性則用lanky來(lái)表達(dá)。