Singular Nouns
* Add an apostrophe and an 's' to most singular nouns:
* dog's bone
* teacher's desk
* child's toy
* If the singular noun already ends in 's', add only an apostrophe:
* James's car (or James')
* boss's office
* For proper nouns ending in 's', you can either add an apostrophe and 's' or just an apostrophe:
* Charles's book (or Charles')
* Jesus' teachings (or Jesus')
Plural Nouns
* If the plural noun ends in 's', add only an apostrophe:
* students' grades
* birds' nests
* babies' toys
* If the plural noun does not end in 's', add an apostrophe and an 's':
* men's shoes
* children's books
* women's rights
Other Notes:
* For compound nouns, add the possessive ending to the last word:
* mother-in-law's advice
* brother-in-law's house
* For joint possession, add the possessive ending to the last noun:
* John and Mary's car (They share the car)
* For individual possession, add the possessive ending to each noun:
* John's and Mary's cars (They each have their own car)
* Avoid using an apostrophe when you are referring to a noun that indicates a plural.
* Incorrect: We need to buy new glasses' for the party.
* Correct: We need to buy new glasses for the party.
Remember, these are just the general rules. There can be some exceptions and variations depending on the context. Always consult a dictionary or grammar guide if you are unsure!