As far as I know, one application of elliptical structure is the omission from a clause one or more elements which has been repeated in previous clauses. However, I do not know whether there exists some specific general rule stating how and when to apply this structure.

Let me be more specific:

  1. Is it correct to say that one can always omit any word which has been repeated before?

  2. Is this structure optional (I have read somewhere that sometimes it is obligatory, for example with cases of comparative deletion (for example, the sentence “More students were in the class today than were there yesterday”), but I also have read somewhere that the omitted words can be added without producing an ungrammatical structure)?

I want to emphasize that I want to know the answer to my question for formal English used in academic writing.


After pondering the useful comments, I conclude that one should not consider any omission of words as ellipsis. In fact, ellipsis is the omission of elements which are understood in the context of the remaining elements and recoverable from the linguistic context. So examples such as “seeing more examples and gaining more experience” and “making more effort and reading more grammar textbooks” cannot be considered as elliptical structures since the second more is not recoverable from the linguistic context (We would have two sentences with different meaning before and after the omission of the second more).

So I think the first question should be rephrased as follows.

1’. Which repeated elements of a sentence can be omitted in order to get an elliptical structure?

  • 2
    In your example, you've performed one repetition (were), and one "substitution" (there = in the class). You can validly omit both (and most people usually would), but it's certainly not valid to delete just the verb. More students were in the class today than there yesterday looks completely invalid to me, but I wouldn't know how to describe the problem in terms of "syntax violation". Commented Mar 26, 2019 at 15:28
  • 2
    I'm also unsure whether it's meaningful to say that your example "deletes" the predictable repeated subject (students) of the potentially deletable verb were. But on reflection, the example given in previous comment is perfectly grammatical. It's just stylistically appalling. Commented Mar 26, 2019 at 15:31
  • 3
    Few things are always in English – especially so with ellipsis, and hence I think the answer is no, a general rule doesn't exist. I would think where ellipsis is optional and felicitous, however, formal English would permit dispensing with it, while informal, everyday English favors as much ellipsis as possible, so long as the meaning gets across.
    – user3395
    Commented Mar 26, 2019 at 15:33
  • 2
    "Omitted words can be added without producing an ungrammatical structure." Adding back omitted words can never be ungrammatical. However, doing so may sound stilted and stylistically awkward in some cases. As in other comments, it's impossible to come up with any kind of general rule. What's idiomatic is simply too broad and, sometimes, illogical. Commented Mar 27, 2019 at 0:28
  • 1
    You say you think the second instance of "more" in by seeing more examples and gaining more experience, which is perfectly true. Well, you can omit it - but if you do, native speakers won't assume the first instance also applies to "experience". Which in practice makes no real difference to the meaning in that exact example. But it would in, say, making more effort and reading [more] grammar textbooks, where presence / absence of the second instance strongly implies you have / haven't already read at least some grammar textbooks. Commented Mar 27, 2019 at 13:42

1 Answer 1


There were some great comments below the question, so I'm going to try to provide an answer that summarises some of that content.*

There is no general rule about when repeated words can be omitted. Learning to be comfortable with when omissions make sense is probably going to be a matter of experience.

But there is a lot of flexibility, even in formal written English, and "the shorter the better" is the general practice in English, so long as ambiguity is not introduced.

So any of the following are grammatical, but the first would be considered cumbersome and unnecessary.

There were more students in class today than there were students in class yesterday.

More students were in class today than were there yesterday.

More students were in class today than yesterday.

One rule that does seem to apply (as far as I can see) is that when the verb changes significantly, you may need to stop omitting words if you want to avoid misunderstanding.

These two sentences (as @FumbleFingers pointed out) do not mean the same thing at all.

I am making more effort and reading more grammar textbooks.

I am making more effort and reading grammar textbooks.

There is no implied "more" with relation to grammar textbooks in the second sentence.

I suspect one of the better grammarians (than me) on this site will be able to explain exactly why. Perhaps a subject for a separate question!

*(Because unanswered questions make my brain hurt.)

  • Have made them full sentences.
    – fred2
    Commented Mar 28, 2019 at 20:26
  • Thank you for your nice answer.
    – Later
    Commented Mar 29, 2019 at 7:52
  • Can you tell me whether your claim “the shorter the better also holds in formal writing (Can you give me any reference)? So, can we say that the sentence “More students were in class today than were there yesterday” is more appropriate for formal writing than the sentence “More students were in class today than yesterday”?
    – Later
    Commented Mar 29, 2019 at 10:07
  • 2
    @Later: I don't think any style guide would actually recommend the longer form for your example there (in general, the maxim less is more applies just as much to formal communications as it does to poetic / literary and relaxed conversational contexts). But some people who aren't used to writing formal text tend to make the "mistake" of being unnaturally verbose / circumloquacious when operating outside their normal linguistic "comfort zone". Don't copy them. Commented Mar 29, 2019 at 13:45
  • 2
    @Later - FumbleFingers explained exactly why using fewer words is the right choice. So long as there is no ambiguity or confusion in your grammar, it is always a good idea to exclude words that don't need to be there. Excluding words doesn't mean 'use short sentences' necessarily, it means 'express yourself in the most concise and clear way possible'.
    – fred2
    Commented Mar 29, 2019 at 13:53

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