Definition:Possessive nouns show ownership. Possessive comes from the same root as possession, something you own.
Add 's to singular words to show possession.
(dog + 's)
(sister + 's)
(car + 's)
If a singular word ends in s, it is still necessary to add 's.
(Charles + 's)
(Bess + 's)
(bus + 's)
If you have added an s to make a word plural (for example, cat ⇒ cats), adding 's will sound ridiculous (cats's). In that case, add only the apostrophe to the end of the word.
(dogs + ')
(sisters + ')
(cars + ')
Just like singular possessives, plural possessives that don't end in s add 's.
(children + 's)
(fish + 's)
(octopi + 's)
Look at the ending in front of the apostrophe to see if the word is singular or plural.
One dog|'s tail
(One dog has one tail.)
Two dogs|' tails
(Two dogs have two tails.)
If two people own something together, use an 's after the second person only.
Joe and Mary's car is new.
(Both Joe and Mary own the car.)
If two people own two separate things, add 's to each name.
Laurie's and Megan's nails are painted the same color.
(Each girl has her own nails.)
You may find that certain names ending in s add only an apostrophe. That rule is somewhat old-fashioned. However, some names, such as Jesus, Moses, Achilles, and Charles Dickens (historical names that end in a z sound), can end with either an apostrophe or 's.
Jesus' parables were instructional stories.
Jesus's parables were instructional stories.
Moses' first tablets were broken.
Moses's first tablets were broken.
Some people prefer to use only the apostrophe, but because we usually pronounce the extra s, adding 's is correct as well.