This is quite hard to explain (and seemingly impossible to search for on Google) so here's an example: In relation to dogs and their owners (masters), I saw this sentence: "Their understanding of the subject is as good as their masters."

Does the word "masters" require a possessive apostrophe, even though the noun "understanding" has been omitted from the end of the sentence in order to avoid repetition?

  • Any chance that the example sentence is comparing how well the dogs understanding the subject to how good (in the sense of compassionate, caring) their masters are? That would be a somewhat strange phrasing but I could see it being used, and that would definitely affect the answer to this question. Some context would probably help establish whether that might be the case.
    – David Z
    Oct 5, 2018 at 4:30

2 Answers 2


In the example sentence, "Their understanding of the subject is as good as their masters," the actual thing being compared is the understanding of their masters. The sentence therefore requires a possessive form for "masters", e.g., "Their understanding of the subject is as good as their masters'."

Which possessive to use (singular or plural) depends on what the sentence is trying to convey. If all the dogs belong to a single master, you would use the single possessive. If the dogs referenced belong to two or more different masters, you would use the plural.

Also, it should be pointed out that the possessive noun form is only required if the sentence is indicating that the noun possesses something. For instance, the sentence, "These dogs are as lazy as their masters!" is correct without the possessive because the sentence is not referring to anything the masters possess.

  • 1
    My cat's coat is prettier than my dog's. Oct 4, 2018 at 16:27
  • 1
    Unless you have two dogs, in which case, your cat's coat is prettier than your dogs'. Or you have two cats who both have prettier coats than your one dog. In that case, your cats' coats are prettier than your dog's. Or, gosh darnit, you have two cats and two dogs but the cats both have prettier coats! Then, your cats' coats are prettier than your dogs'.
    – R Mac
    Oct 4, 2018 at 16:29
  • 1
    My mistress' eyes are larger than yours. Oct 4, 2018 at 17:32
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    @MichaelHarvey How many syllables are in the word mistress'? When I speak the possessive form of mistress it has three syllables, so I would write it so that it looks as if it should have three: mistress's.
    – JeremyC
    Oct 4, 2018 at 21:34
  • 1
    In my previous comment here, both "mistress's" and "mistresses'" are correct; the former is singular possessive and the latter plural possessive. The bit about being curious which it is was a cheeky reply to the question, i.e., does he have one mistress or many?
    – R Mac
    Oct 5, 2018 at 2:35

Whilst I agree with the answer given by @R Mac, that the plural possessive apostrophe is required, I don't think I would write it like that, and certainly I wouldn't say it.

The problem is that the apostrophe is needed simply to provide grammatical clarity. And when speaking a listener cannot perceive the apostrophe.

I would say: Their understanding of the subject is as good as that of their masters.

  • Would it be correct to call this an example of the possessive genitive ?
    – Nigel J
    Oct 5, 2018 at 0:17
  • The word "genitive" is defined, at least in the Google dictionary, as an "indicator of possession, or close association". So the term "possessive genitive" would seem tautological to me.
    – WS2
    Oct 5, 2018 at 6:45
  • I meant that this is the genitive of possession rather than the genitive of origin (or 'source' as the OED describes it).
    – Nigel J
    Oct 5, 2018 at 12:02

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