List of English auxiliary verbs

The following English verb forms can appear as auxiliary verbs. Note that some of these forms can also be used as main verbs. The main criterion for whether something is an auxiliary verb used here is whether it participates in subject-auxiliary inversion.

* "am", "are not" ("aren’t") (only in inversion, as in "Aren't I special?"), "ain't", " 'm" (as in "I am" or "I’m")
* "are", "are not" ("aren’t"), "ain't", " 're" (as in "you're" or "you are")
* "be" (NB: this is an infinitive/imperative form and as such does not participate in subject inversion or tag questions)
* "been"
* "can", "cannot" (does not invert), "can't"
* "could", "could not" ("couldn’t")
* "did", "did not" ("didn’t")
* "do", "do not" ("don’t")
* "does", "does not" ("doesn’t")
* "had", "had not" ("hadn’t"), " 'd" (as in "She’d gone out" or "She had gone out")
* "has", "has not" ("hasn’t"), " 's" (as in "She's gone out" or "She has gone out")
* "have", "have not" ("haven’t"), " 've" (as in "I've" or "I have")
* "is", "is not" ("isn’t"), " 's" (as in "She's back" or "She is back")
* "may", "may not" ("mayn’t")
* "might", "might not" ("mightn’t") (rare in American English)
* "must", "must not" ("mustn’t") (rare in American English)
* "ought", "ought not" ("oughtn’t")
* "shall", "shall not" ("shan’t") (rare in American English)
* "should", "should not" ("shouldn’t")
* "was", "was not" ("wasn’t")
* "were", "were not" ("weren’t")
* "will", "will not" ("won’t"), " 'll" (as in "she'll" or "she will")
* "would", "would not" ("wouldn’t"), " 'd" (as in "I'd go out" or "I would go out")

The contracted forms can be stacked, e.g. "I'd've (I would have) told her to leave", or "She'll've (She will have) left already by the time you get there".

The forms of "dare", "need", and "ought" are sometimes considered auxiliaries, but they do not permit subject-auxiliary inversion in many dialects. If they are auxiliaries, they permit sentences such as "Dare you go?" ("Would you dare to go?"), "Need you say this?" ("Do you have to say this?"), and "Ought we go through with this?" ("(Do we have to / Should we) go through with this?").

The contracted form " 'ma" from African American Vernacular English is increasingly used in Standard American English, as in "I'ma tell her to leave" (approximately, "I will tell her to leave").

In some British English dialects, "iz" (not usually written) is the main auxiliary form, replacing "is", "has", "was", and possibly others.