An apostrophe appears as part of a word to show possession or to indicate the omission of one or more letters (a contraction). Despite this sounding straightforward, it can be confusing even for the native speaker. The two cases are illustrated below.
- The most common way to form a possessive in English is to use an apostrophe ' and s.
(1) The student's article was published in a well recognised magazine.
(2) Sweden's popularity is growing in global marketing.
- When the name of the possessor ends in an s, we may write either s's or s' (consider the relevant style guide, if there is one).
(3) Professor James' lecture was enlightening.
(4) Professor James's lecture was enlightening.
- When the possessor ends in a regular plural -s, we only add an apostrophe.
(5) Research shows that wolves' habits have changed in recent years.
- If two people possess the same item, an apostrophe and s is used after the second name.
(6) Persson and Lindberg's article argues that .......
- If indicating separate ownership, use an apostrophe and s after both.
(7) Persson's and Lindberg's articles argue that......
Denoting omission of one or more letters (a contraction)
More informal language uses contractions where one or more letters are replaced by an apostrophe. Formal academic writing standards do not recommend using contractions; however, informal emails and less formal writing uses contractions frequently.
Here is a list of the most common ones (by the way, if you want to sound more like the native speakers, use contractions when speaking and reading in English, regardless of the spelling, except in very formal contexts, or when you actually want to stress the part that would otherwise have been contracted):
I'm (short for I am)
I've (short for I have)
I'd (short for I would; I had)
I'll (short for I will)
you're (short for you are)
you've (short for you have);
you'd (short for you would; you had)
you'll (short for you will)
he's (short for he is; he has; he was)
he'd (short for he had; he would)
he'll (short for he will)
she's (short for she is; she has; she was)
she'd (short for she would; she had)
she'll (short for she will)
it's (short for it is; it has; it was)***
we're (short for we are)
we've (short for we have)
we'd (short for we would; we had)
we'll (short for we will)
they're (short for they are)
they've (short for they have)
they'd (short for they would; they had)
they'll (short for they will)
isn't (short for is not)
aren't (short for are not)
can't (short for cannot)
couldn't (short for could not)
don't (short for do not)
doesn't (short for does not)
who's (short for who is; who has; who was)*
who'd (short for who would; who had)
who'll (short for who will)
that's (short for that is; that has; that was)
that'll (short for that will)
won't (short for will not)
wouldn't (short for would not)
shouldn't (short for should not)
needn't (short for need not)
* Be careful not to confuse a contraction with a possessive pronoun
(8) It's the first term of my studies. (contraction = it is)
(9) The university and its grounds are breathtaking. (possession)
(10) Who's going to the conference? (contraction = who is or who was)
(11) Students whose main aim is to gain international experience, are more competitive. (possession)