The apostrophe is used to show ownership. Most of the time, it presents no confusion:
- Bob’s bassoon
- The woman’s finger
- My son’s toys
The tricky part is using an apostrophe when the owner is plural.
RULES FOR APOSTROPHES
1. If the plural noun doesn’t end in -s, add an apostrophe and -s, as shown above. (This is the easy part.)
- the bacteria’s growth
- the mice’s hairballs
2. If the plural noun ends in -s, just add an apostrophe.
- the babies’ bottoms
- the horses’ hooves
- the politicians’ promises
3. If the word is a proper noun that ends in -s, add an apostrophe and an -s. (This is the part people get wrong). Use ONLY with proper nouns. All other plurals should follow the rule above.
- Yeats’s poem
- Ross’s riddle
- Chris’s crisis
An alternate way to express the possessive for proper nouns already ending in -s is to simply put the apostrophe at the end of the -s.
- Yeats’ poem
- Ross’ riddle
- Chris’ crisis