An apostrophe is the mark ' when it is written to indicate that one or more letters have been left out of a word, as in 'isn't' and 'we'll'. It is also added to nouns to form possessives, as in 'Mike's car'.
英漢詞典釋義
n.
撇號；省略符號；所有格符號
When do I need to use an apostrophe?什么時候用撇號？Answer these questions, using the words in parentheses. Put the apostrophe in the right place.用句后括號中的詞或詞組來回答問題，注意撇號的位置。
英英詞典釋義
Noun
1. address to an absent or imaginary person
2. the mark (') used to indicate the omission of one or more letters from a printed word