Use an apostrophe to show possession with a noun. For singular nouns or plural nouns that do not end in ‘s,’ just add an apostrophe and an ‘s.’
The boy’s bike . . .
The adolescent’s tricycle . . .
The children’s toys . . .
The turtle’s shell . . .
If you want to show possession with a plural noun than ends in an ‘s,’ add an apostrophe after the ‘s.’
The boys’ bikes . . .
The adolescents’ tricycles . . .
The turtles’ shells . . .
Use an apostrophe to mark the omission of letters or numbers in a contraction or a date.
cannot = can’t (the apostrophe shows that the ‘n’ and ‘o’ have been left out)
I am = I’m
the class of 2010 = the class of ’10
An apostrophe can be used to form the plurals of letters, words, or lowercase abbreviations if confusion might result from using ‘s’ alone.
When I was alphabetizing names, I had no q’s or z’s.
Please distinguish your I’s from the number 1.
Did you get any c.o.d.’s today?
In general, add only ‘s’ in roman (regular) type when referring to words as words or capital letters.
You used six ‘ands’ in the first sentence.
My son got two As and four Bs on his report card.
Do NOT use an apostrophe for plurals of abbreviations with all capital letters (DVDs, CDs,) or a final capital letter (ten Ph.D.s) or for plurals of numbers (9s, the late 1960s).
Do NOT use an apostrophe to show possession with pronouns:
That box is hers.
The turtle is his.
The cat licked its paw.
Thanks to Bonnie Crowder, of Idearella.com, we have an additional tip for using apostrophes.
Do NOT put an apostrophe alone on a singular noun ending in S.
For example, “My dress’s seam has a rip” is correct.