I've been confused about the following sentence. I can't find a subject and a verb, and I can't understand why "would" is here. Can anyone tell me the structure of this sentence?

Only when that unit is complete would you begin to think about the second most critical element on the page.


2 Answers 2


The structure is:

"only" + [adverbial] + [verb with tense] + [subject] + [the rest].

The adverbial is "when that unit is complete", "would" is the verb with tense, and the subject is "you".

A simpler way of phrasing the same sentence is:

You would only begin to think about the second most critical element on the page when the unit is complete.

Other examples of sentences with this structure:

"Only then did she understand her true power."
"Only after the dealer finishes dealing out all the cards should you look at your hand."
"Only with strong medicine can I sleep through the night."

With this structure, as with many others in English, the subject and its verb are switched.


Also read rjpond's answer for info on inverted structures in English beyond just "only...".

  • Thanks for your answer! One question: if "would" is a verb, why is the subject and the verb order switched? Maybe I don't understand the "verb with tense". If so, could you let me know if there are any web pages that explain it?
    – Inclu Cat
    Commented Sep 20, 2021 at 3:07
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    There are many structures in English where the subject and verb order are switched. The most common one is a question: in the question "Are you OK?", "are" is the verb, and it comes before the subject. When I said "verb with tense", I meant that the verb that goes with the subject of a sentence always has tense. It's not that important to focus on for this question, but just putting "verb" felt incomplete to me
    – gotube
    Commented Sep 20, 2021 at 4:17
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    @IncluCat when sentences begin with the negative sounding words such as "only", "not only", "never", "hardly", "seldom", and "not until" then the subject comes after the auxiliary, e.g. "Not until I reached home, did I realise I left my home keys at work.” it's called inversion.
    – Mari-Lou A
    Commented Sep 20, 2021 at 8:52
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    @IncluCat The actual verb in that part of the sentence is not just would but would begin, split by the subject you. Commented Sep 20, 2021 at 14:42
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    @RossPresser "Would" is indeed a helper (or "auxiliary") verb. There's no limit to the number of verbs in a clause. However, other than with compound verb phrases (like "eats, shoots and leaves"), there can only be one verb with tense that goes with the subject of that clause. All the other verbs in the sentence have roles other than providing tense. "A tribute would have to have been payed on a regular basis", for instance, has five verb forms, only one of which, "would", has tense.
    – gotube
    Commented Sep 21, 2021 at 0:38

I have upvoted the existing, excellent answer, but just to add:

  • Other than in questions, most subject/verb inversion is rare in informal use.
  • Another notable trigger for subject-verb inversion is the use of a negative adverb at the start of the sentence, as in "Never had I seen such a thing", "Rarely have I heard such utter nonsense", or "Hardly had I reached the top of the hill when I saw her".
  • Further information can be found at https://www.bbc.co.uk/learningenglish/course/towards-advanced/unit-25/session-1 :
    • "Inversion happens in English for emphasis, dramatic purpose or formality. This type of inversion uses negative and limiting adverbs - these are a group of adverbs which limit the meaning of a verb or make it negative. Examples are never, hardly, no, only... and there are others (see grammar page for more details). To invert a sentence move the adverbial to the beginning of the sentence and invert the subject and auxiliary verb."
  • Also worth looking at: https://dictionary.cambridge.org/grammar/british-grammar/inversion:
    • "In formal styles, when we use an adverb with negative meaning (e.g. never, seldom, rarely, scarcely, hardly) in front position for emphasis, we invert the subject (s) and auxiliary (aux)/modal verb"
  • There are interactive exercises at https://elt.oup.com/student/englishfile/advanced3/grammar/file04/grammar04_b01?cc=se&selLanguage=en

Just in case you have an interest in linguistics: English is a Germanic language, sharing a common ancestor language with German, Dutch, Swedish, Danish, etc. A common feature of Germanic is the V2 (verb in second place) rule. English is unique among Germanic languages in having abandoned this rule, but the rules about "only" and negative adverbials are remnants of this V2 pattern. In other Germanic languages the rule applies much more consistently, so people say the equivalent of *"Quietly entered I the room" rather than "I quietly entered the room".

  • Now I understand what name of the rule and its purpose. And the information about linguistics is very interesting! Thank you!
    – Inclu Cat
    Commented Sep 21, 2021 at 2:37

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