noun

The word "apostrophe" is punctuation Mark: A small symbol (') used in writing to show possession (e.g., Jane's book) or to indicate the omission of letters in contractions (e.g., don't for do not).

Example

1. Please don't forget the apostrophe in "it's" to show that it means "it is".
2. The apostrophe in "John's bike" indicates that the bike belongs to John.
3. The teacher corrected the student's essay and added an apostrophe to show possession.