I can’t tell one twin from the other.我分不出雙胞胎中誰是誰.
I spoke to both of the twins this morning.今晨我與兩個雙胞胎都談了談.
類似地,parent指父母之壹,即指父親或母親,要表示父母雙親,應用復數parents.比較：
A half-brother is brother with only one parent in common with another half-brother指同父異母或同母異父的兄弟.
The parents named their baby Tony.父母給他們的孩子取名托尼.
（摘自《英語常用詞多用途詞典》twin詞條,金盾出版社）