I found a sentence in my "Preparation and Practice Exam TOEFL" book a sentence states "Not until 1895 did Cornell University begin to offer a degree in ornithology" . anyone can explain what the word "did" means in the sentence? I mean, as we know "did" is a verb and should have a subject, but in that sentence I found that the subject is "Cornell University" and its verb is "begin". so why does "did" in the sentence exist? what for?

1 Answer 1


Moving some kinds of 'adjunct' (modifying) phrases from their usual position to the front of a sentence triggers subject-auxiliary inversion, just as in questions. Most negative adjuncts, including those with only, do this:

I will go.
→ [inversionWill I] go?

I will go only if I am paid.
→ Only if I am paid [inversionwill I] go.

If there is no auxiliary in the ordinary form of a sentence, "Do support" is required: the appropriate form of do is brought in as a 'dummy' to supply the auxiliary needed for inversion.

Cornell offers a degree in ornithology.
→ [inversion + do-supportDoes Cornell] offer a degree in ornithology?

This, too, occurs with fronted negative adjuncts:

Cornell began to offer a degree in ornithology only in 1895.
→ Only in 1895 [inversion + do-supportdid Cornell] begin to offer a degree in ornithology.

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