I have came across such sentence:

By now, Queen Elizabeth II has been on the throne for an astounding 67 years.

Why do we use "an" here, even though 67 years is plural?

  • 3
    Does this answer your question? "A dreadful five minutes" - what about the article?
    – Laurel
    Commented May 8, 2021 at 21:11
  • 1
    [Tanya: I have come across a sentence like this or this sentence. "such sentence" is not right.]
    – Lambie
    Commented Aug 28, 2023 at 16:20
  • Please link to the place where you came across the sentence
    – James K
    Commented Apr 24 at 17:11

2 Answers 2


This is a special case of simple agreement override that happens when a measure phrase is interpreted as a single measure (of time, money, or distance). So in this case, "an astounding 67 years" is understood as a single, continuous time period.

Huddleston & Pullum (2002) discuss this under § 18.3 Further Override and Alternations:

18.3 Further Override and Alternations

(a) Measure Phrases
We have already noted that plural measurement nominals can be respecified as singular for the purposes of agreement and selection within the NP. This carries over to subject-verb agreement, whether or not there is any marker of singular number within the NP:

[14] i That ten days we spent in Florida was fantastic.
ii Twenty dollars seems a ridiculous amount to pay to go to the movies.
iii Five miles is rather more than I want to walk this afternoon.
iv Three eggs is plenty.

This is the opposite of the collective override: here an NP that is formally plural is conceptualised as referring to a single measure (of time, money, distance, or whatever) and accordingly takes a singular verb. The measure override is characteristically found with be or other complex-intransitive verbs (such as seem in [ii]). In [ii], where the predicative complement is a singular NP, the override is obligatory (*Twenty dollars seem a ridiculous amount to pay); in [iiii-v] it is optional but quite strongly preferred.


By now, Queen Elizabeth II has been on the throne for an astounding 67 years.

If you can give X an attribute such as "astounding", you "which"-ify it - meaning you are indirectly acknowledging there is a possibility that one X is astounding and another X is not astounding or something other than astounding.

The speaker/writer does not expect the listener/reader to know "which 67 years" beforehand, so the indefinite article is used, and not the definite article.

In this sentence, the indirectly acknowledged choices for X where the question "which X" would have to choose from could be any other possible attributes of 67 years, e.g. "an astounding 67 years" versus "a terrible 67 years", "an uneventful 67 years", etc.

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