Section 11.5 Negation
Negation—making a sentence mean its opposite—works differently depending on whether the verb phrase contains an auxiliary or not. Understanding how negation interacts with modals and auxiliaries is essential for forming correct sentences and for recognizing the sometimes surprising differences in meaning that negation creates.
Negating Modals.
Modals negate by adding not directly after the modal. No additional auxiliary is needed:
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She cannot attend. (or can’t)
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You must not enter. (or mustn’t)
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He should not have left. (or shouldn’t)
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They will not agree. (or won’t)
Note that won’t is the contracted form of will not—one of the few irregular contractions in English.
Negating Primary Auxiliaries.
Primary auxiliaries (be, have, do) also negate by adding not directly:
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She is not running. (or isn’t)
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They have not finished. (or haven’t)
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He was not invited. (or wasn’t)
Negating Main Verbs: Do-Support.
When a sentence has no auxiliary or modal, English cannot simply add not after the main verb. Instead, it inserts the auxiliary do to carry the negation—a process called do-support:
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She likes coffee. → She does not like coffee. (not
She likes not coffee.) -
They arrived on time. → They did not arrive on time.
Notice that when do carries the tense, the main verb returns to its base form: She likes → She does not like (not does not likes).
Negation and Meaning Shifts.
Negating a modal does not always produce the meaning you might expect. Two cases are especially important:
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must not = prohibition (you are forbidden): You must not enter the building.
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don’t have to = no necessity (you are free not to): You don’t have to enter the building.
These mean very different things. Must not says the action is prohibited; don’t have to says the action is optional. Similarly:
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may not = refusal of permission: You may not leave early.
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might not = possibility of not happening: She might not come to the party.
