a.

1. 同一的
   She wore the identical dress on both occasions.

   她在两个场合穿戴同一套衣服。

2. 完全相同的，完全相似的[（+to/with）]
   The two words are identical in meaning.

   这两个字的字义完全一样。

   His hat is identical to mine.

   他的帽子同我的一模一样。

3. （双胞）一卵的，同卵的；同源的

adj.

1. exactly alike.
   ▸(of twins) developed from a single fertilized ovum, and therefore of the same sex and usually very similar in appearance. Compare with fraternal (in sense ³).
2. Logic  & Mathematics  expressing an identity.