If a word is singular, use an apostrophe and an s to make it possessive.
- The dude’s car was just cleaned.
- She didn’t like her boss’s attitude.
- John’s computer is broken again.
If a word is plural, use an apostrophe after the s to make it possessive.
- She must give two weeks’ notice.
- All the students’ grades were above average.
- The businesses’ owners were all upset.
For irregular plural words, use an apostrophe and an s.
- It’s in the men’s section.
- Those are children’s shoes.
For collective possession, use an apostrophe with the final noun.
- Look at Jerome and Gloria’s new car.
- That’s his mom and dad’s house.
For individual possession, use an apostrophe with each noun.
- They compared California’s and Arizona’s tap water.
- He memorized Allen’s and Maria’s phone numbers.