By Marina Pantcheva
The apostrophe has two functions: it marks possession, and it is used in contractions to indicate the place where the letters have been omitted.
In singular, possession is marked by ’s, written immediately after the possessor.
(1) John’s car
(2) the boy’s toy
Important: there is no apostrophe before the possessive –s with pronouns.
(1) its, hers, yours, ours
If the possessor is expressed by more than one word, ’s comes after the last word.
(3) my late brother’s wife
(4) Mr. Johnsen’s house
(5) Charlie and Lola’s new room. (the room belongs to both Charlie and Lola)
Use ’s with singular possessors that end in –s or –z.
(6) Charles’s books
(7) Sanchez’s horse
Plural possessors that end in –s take only the apostrophe. Plural possessors that end in some other letter take ’s.
(8) the boys’ toy
(9) the Sanchezes’ horse
(10) the children’s bikes
Importantly, it is the written letter that determines whether to place just an apostrophe or ’s after a plural. There are a few English nouns that end in the sound /s/ or /z/ but are written with a final –e: mice (mouse) dice (die), geese (goose). Such plural nouns take ‘s is the possessive form.
(11) the geese’s feathers
(12) mice’s teeth
In other words, the possessive –s is required after a singular word ending in -s but not after a plural word ending in –s.
|ending in –s, –z||’s||’|
|not ending in –s, –z||’s||’s|
The apostrophe is used with contractions and is placed at the spot of the omitted letter(s). Words that often are written in contracted form are: be, have (-’ve), has (-’s), had (-’d), will (-’ll), would (-’d), and the negative particle not (n’t). For a full list of the standard contractions, follow this link. Some common contractions are shown below.
(13) I am = I’m
(14) you are = you’re
(15) he is = he’s
(16) she is = she’s
(17) it is = it’s
(18) we are = we’re
(19) they are = they’re
(20) do not = don’t
(21) does not = doesn’t
(22) cannot = can’t (cannot is written as one word)
(23) should not = shouldn’t
(24) could not = couldn’t
(25) shall not = shan’t
(26) will not = won’t
(27) I have = I’ve
(28) I had, I would, and I should = I’d
(29) I will and I shall = I’ll
Avoid the apostrophe to mark possession with pronouns
A very common mistake is to place an apostrophe in the possessive form of pronouns like its, yours, hers, ours, theirs. Although this makes perfect sense, it is considered wrong.
(31) I’ve lost my pen. May I borrow yours?
(32) The book is old; its pages have turned yellow. [correct]
(33) The book is old; it’s pages have turned yellow. [incorrect, it’s is a contraction of it is]