Even a small amount of gases have / has a large effect.

This sentence is an exerpt from a reading passage, which is talking about CO2 in global warming. It says CO2 accounts for only 0.038% in the atmosphere, and then the example sentence 'Even a small amount of gases have / has a large effect.' appears.

  • Which is the most appropriate answer?

    1. If gases is the subject, and it is plural, the correct answer would be 'have'.

    2. If the subject is a small amount, then the answer would be 'has'.

What do we see as the subject here? Can both be the subject?

  • @Chappo There is absolutely nothing wrong in asking for help with work on here so long as you clearly identify what aspect of the work is confusing you and causing you problems. Please delete your comment as it could mislead readers. Thanks. Jun 28, 2016 at 15:23
  • @Chappo The comments above are correct. A proofreading question is a question like "please proofread the following paragraph". This question is not like that.
    – MetaEd
    Jun 28, 2016 at 15:42
  • 1
    @Mari-LouA, MετάEd, Chappo: Shall we all delete our comments here? Jun 29, 2016 at 23:56

2 Answers 2


The subject can only be amount, since gases is part of a prepositional phrase describing amount. The number of the verb's going to follow the number of the subject, hence it should be singular has.

  • Correct. The key point is that the object of a preposition is never the subject of a sentence. The verb must match the subject.
    – MetaEd
    Jun 28, 2016 at 15:56
  • @MετάEd Almost never, because there are troublesome beasts like a number of to prove the rule. Jun 29, 2016 at 19:42
  • @Araucaria Thank you for your answer. And your example 'a number of~' was the very thing that I was wondering about. Could you tell me what makes the difference between the two? Or should I just understand the case 'a number of ~' as an idiom? Thank you again for your answer.
    – VCCine
    Jun 29, 2016 at 23:43
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    When it comes to phrases with the word number, the rule is that the number is always singular, while a number is always plural.
    – Nick
    Jun 29, 2016 at 23:50
  • Sorry, VCCine, I'm mega-busy right now (I''m in trouble!), but maybe @MετάEd will help you with this one :) [nudge, nudge MετάEd!] Jun 29, 2016 at 23:51

In written English, the formal subject of the sentence (here, amount) will almost always be referenced and grammatical agreement/concord requires has.

The same is true for spoken English. However, it is possible that some speakers might say have because of the proximity of the word gases. This does not make gases the subject.

In short, use has.

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