Examples of some of the most common contractions in the English language include isn't, aren't, wasn't, weren't, didn't, don't, wouldn't, couldn't and o'clock. Others are can't, there's, that's, what's, he's, they've and who's. Contractions join two or more words by deleting certain letters and replacing those letters with an apostrophe.
Several of the common contractions have a form of the verb "to be" as their base with "not" added to the word, putting an apostrophe in the place of the letter "o." Others are made by combining helping verbs such as do, does, did, has, have, had, could, would or can with the adverb "not," again substituting an apostrophe for the "o."
A contraction used frequently throughout the day to tell time is the word o'clock. It is actually a contraction of the three words "of + the + clock," with the letters "f" and "the" replaced with an apostrophe.
Other common contractions are formed using pronouns as the base word. Personal pronouns such as I, you, he, she, it, we and they combine with forms of the verb "to be" or helping verbs such as forms of will or have to make contractions. Examples are she's (she is), you'll (you will) and I've (I have). Other pronouns, such as that or who, form contractions in a similar fashion.