List of auxiliaries in English Diagnostics for identifying auxiliary verbs in English

Vs. light verbs[edit]

Some syntacticians distinguish between auxiliary verbs and light verbs.^[19][20] The two are similar insofar as both verb types contribute mainly just functional information to the clauses in which they appear. Hence both do not qualify as separate predicates, but rather they form part of a predicate with another expression - usually with a full verb in the case of auxiliary verbs and usually with a noun in the case of light verbs.
In English, light verbs differ from auxiliary verbs in that they cannot undergo inversion and they cannot take not as a postdependent. The verbs have and do can function as auxiliary verbs or as light verbs (or as full verbs). When they are light verbs, they fail the inversion and negation diagnostics for auxiliaries, e.g.
Note that in some dialects (for example, the West and South West dialects of Hiberno-English), the inversion test may sound correct to native speakers.
a. They had a long meeting.
b. *Had they a long meeting? - Light verb had fails the inversion test.
c. *They had not a long meeting. - Light verb had fails the negation test.
a. She did a report on pandering politicians.
b. *Did she a report on pandering politicians? - Light verb did fails the inversion test.
c. *She did not a report on pandering politicians. - Light verb did fails the negation test.