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What is the correct possessive for nouns ending in s?

I want to write this sentence:

In a singleton pattern, a class's constructor needs to be private instead of public.

it is correct to write:

  • a classes constructor
  • a class' constructor
  • a class's constructor
  • a classes' constructor

marked as duplicate by waiwai933, Hellion, RegDwigнt Mar 9 '11 at 10:37

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That would be class' or class's, but I would rather change the sentence to avoid that altogether.

Also, as it's a specific pattern that is applied to a specific class, it would be more correct to refer to the pattern and the class instead of a pattern and a class:

In the singleton pattern, the constructor of the class needs to be private instead of public.

As the pattern is something that only is applied to a class, it can even be implied:

In the singleton pattern, the constructor needs to be private instead of public.

  • 1
    Poor singleton! It is (indirectly) associated with "just avoid it altogether" even in the English Stack Exchange! – Andrew Grimm Jun 27 '11 at 6:20

The Chicago Manual of Style, 14th edition says:

6.19: The possessive of singular nouns is formed by the addition of an apostrophe and an s [...]

There are a few exceptions listed later on, but they do not apply to a common noun ending in s (or ss).

Thus I say that

a class's constructor

is correct.


Both "a class' constructor" and "a class's constructor" are accepted as correct. More recent English use stylistic guides show preference for the "a class's constructor" use.

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