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This article/section is a stub — probably a pile of half-sorted notes and is probably a first version, is not well-checked, so may have incorrect bits. (Feel free to ignore, or tell me)


Apostrophe, the punctuation mark

An apostrophe represents something that is missing, be it letters or sounds (see contraction, elision), and others).

The easiest rule-o'-thumb about when to use an apostrophe is "can you think of such an expansion?".

This is hardly complete or foolproof, but it's a good start.


  • The possessive use of 's has morphologized long ago, so there is no longer an expansion.
For example, when an apostrope basically indicates 'their', e.g. in "children's toys", there is no obvious expanded form without having to reorder the sentence.
  • Agreement may not be as strictly enforced in contractions.
For example, "There's more details" isn't considered wrong, and is somewhat preferred over "there're more details" because of easier pronunciation. ...while in non-contracted form form you would always go for are, not is.
  • In reading, context is often most informative:
following 's with a noun suggests possession,
following 's with a verb often indicates a contraction with 'is'.
A few cases could be interpreted both ways, and determining the correct reading may depend on the sentence around it.

Apostrophe as contraction


  • don't (do not)
  • hadn't (had not)
  • let's (let us)
  • it's raining (it is raining)
  • it's been raining (it has been raining)
  • my pet's funny (my pet is funny)
  • you're (you are)
  • who's who (who is who)
  • they're (they are)
  • they'd (they had)
  • gov't (government) (contraction in a slightly wider sense than most of the above)

Some are easily and commonly confused, particularly those with homophones, particularly its/it's, your/you're and their/they're. Perhaps this is caused by apostrophe use coming partly but not only from function - for example, the possessive its form can replace possessive Noun's forms - but these two are distinct from it's.


Example: Kate's fish

It is useful to realize that 's is only possessive on nouns, never on pronouns like 'it' and 'you', 'they' and such.

Additionally, 's is never used to (some people confused about apostrophes try this)

  • conjugate verbs,
  • mark plurals

(Technically, the omission→apostrophe test also holds for possession, but only linguists will appreciate how: Middle English had the -es suffix for posessives, as many germanic-based languages did (modern German still does). For example, Middle English wrote "Kynges court" where we would write "King's court." The former form doesn't exist anymore; you could say apostrophe-s has essentially become a morphologized construction. For the "expanded it and see if it makes sense" test to work you would need to pretend that this old form still exists.)

Possession with esses and plurals

Consider: Kansas' and Kansas's, boy's and boys's

When a word ends in an s (or x), you can mark it possessive with an apostrophe-s, or just the apostrophe.

There are no hard rules about this, this is largely a style issue, though lessening possible ambiguity is often part of the reasoning.

It seems that more people seem to prefer 's.

When a noun can be pluralized or not, things become a little more complex. For example:

  • The boy's collection means a collection owned by a single boy
  • The boys's collection means one collection from multiple boys
...and some styles would prefer The boys' collection

Apostrophe as phonetic indication

This article/section is a stub — probably a pile of half-sorted notes and is probably a first version, is not well-checked, so may have incorrect bits. (Feel free to ignore, or tell me)

The uses above (contractions, possession) are primarily syntactic, there are also languages in which apostrophes are largely indicators relating to pronunciation.

It is seen indicating a glottal stop, though more often in transcription than in natural writing systems.

In e.g. Dutch, where (diphones aside) there are long/tense and short/lax pronunciations of certain vowels based on context, and apostrophe forces the long/tense form, and is used to write the correct pronunciation.

Acronyms, letters, figures

This article/section is a stub — probably a pile of half-sorted notes and is probably a first version, is not well-checked, so may have incorrect bits. (Feel free to ignore, or tell me)

These rules are not highly standardized or agreed on. Linguists and style guides may disagree with each other.

Most agree acronyms are to be treated as the fully pronounced words, so plurals of words would generally not have apostrophes. For example CDs, MPs, ABCs, IOUs, 1960s and 747s.

...and not CD's, MP's, ABC's and IOU's, 1960's and 747's, though some of these are abused so widely that using apostrophes has become somewhat acceptable. There are also things that are less formal at best, only being settled in style guides and possibly with some conflicting rules between different such guides.

You would add apostrophes when it's actually the contraction or possession case. For example, "The CD's hole" or "That CD's weird" or "the PCs's fans are broken" (PCs being used as a collective plural, and then referring to the fans they have).

Further cases:

  • add an apostrophe on single letters, say "A's and u's".
When arguing this from possible confusion, some say that this is only necessary on lowercase values (particularly for vowels, e.g. u's/us) but not necessary on capitals, as in As.
  • similarly, add on symbols and digits: &'s and 9's. Note that many style guides suggest numbers under about ten should be spelled out as words. When you would use 's to indicate magnitudes, you should probably do the same.

And fuzzier cases:

  • add an apostrophe when an acronym ends with an s, as in SOS's instead of SOSs(verify).
...though some would argue for SOSes instead
  • add an apostrophe when there is internal punctuation, as in Ph.D.'s.
Also occasionally claimed as being anachronistic style, though. (verify)
  • add an apostrophe when there is other possible confusion or ambiguity. (verify)
Examples tend to be arguable.

...but keep in mind that style guides vary.

Apostrophe, the literary device

A speaker or writer directing speech to an imaginary person or abstract quality or idea. (Similar to personification)



The Dutch apostrophe(-as-in-punctuation) rules are primarily about pronunciation.

The basic rule is that if the vowel sound would change in the natural pronunciation of the new word, add an apostrophe to avoid that.

The complete rules, with exceptions, are almost as complex as the English ones.

See also