Do/does/did in questions and negatives
Definition
Do-support uses do, does or did as an auxiliary to form questions and negatives when the verb phrase does not already contain another auxiliary or modal. The main verb remains in the base form.
Examples
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Where do you live?
Do carries the present-tense question structure for the subject you.
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She does not work on Fridays.
Does carries present tense and third-person singular agreement, while work stays in the base form.
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Did they arrive on time?
Did carries the past tense, so arrive remains in the base form.
Do-support vs. an existing auxiliary
Do you understand?
The lexical verb understand has no other auxiliary, so do forms the question.
Are you waiting?
The progressive already contains are, so no form of do is added.
Use do-support only when the verb phrase lacks another auxiliary or modal that can form the question or negative.
The verb be normally forms its own questions and negatives
Main-verb be does not normally use do-support. Questions invert the subject and be, while negatives add not directly.
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Are they ready?
Are moves before the subject without do.
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They are not ready.
Not follows the form of be directly.
Common mistakes
Does she works here?
Does she work here?
After does, the main verb uses the base form work.
Did they arrived late?
Did they arrive late?
Did carries the past tense, so the main verb remains arrive.
Quick check
Question 1 of 3
Which present simple question is correct?
Use does + subject + base verb for a third-person singular present simple question.Which past negative is correct?
After did not, use the base form arrive.Which question does not use do-support?
The progressive verb phrase already contains the auxiliary are.Nice work — you've completed the quick check.
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