The simple present and simple past of the auxiliary verb DO are frequently contracted with the negative adverb not. To form these contractions, do, does, or did are joined to the adverb not and the letter o in not is replaced with an apostrophe.
|I do not believe you.||I don’t believe you.|
|She does not know.||She doesn’t know.|
|We did not go.||We didn’t go.|
The verb DO can be contracted with not to ask Yes / No questions.
|uncontracted||contracted (more common)|
|Do you not hear the train?||Don’t you hear the train?|
|Does she not like Tom?||Doesn’t she like Tom?|
|Did we not pass the test?||Didn’t we pass the test?|
Note that in the uncontracted form, the subject comes before the adverb not. In the contracted form, which is much more common, the subject follows the contraction.
In informal speech, did is often contracted with wh– question words. Note that the first two letters of did are replaced with an apostrophe.
|Who did you see?||Who’d you see?|
|What did she play?||What’d she play?|
|When did you start?||When’d you start?|
|Where did they go?||Where’d they go?|
|Why did he laugh?||Why’d he laugh?|
|How did we get here?||How’d we get here?|
In spoken English, contracted forms are used much more frequently than uncontracted forms.