This article is from the alt.usage.english FAQ, by Mark Israel firstname.lastname@example.org with numerous contributions by
218 Where to put apostrophes in possessive forms: Nouns
1. The standard rule: Use 's for the singular possessive, and a
bare apostrophe after the plural suffix -s or -es for the plural
possessive. For example:
Nominative dog dogs
Possessive dog's dogs'
2. Nouns ending with an [s] or [z] sound (this includes words ending
in "x", "ce", and similar examples): The plural suffix is -es
rather than -s (unless there's already an "e" at the end, as in
the "-ce" words), but otherwise the rule is the same as above:
Nominative class classes
Possessive class's classes'
(The possessive plural is what is wanted in "the Joneses'".
This is short for "the Joneses' house", which is not "the
There are, however, examples where the singular possessive suffix
is a bare apostrophe:
Nominative patience patiences
Possessive patience' patiences'
(In most such examples, the plural is rarely used.) For nouns in
this category, many people would consider the 's suffix and the
bare apostrophe to be acceptable alternatives. The rules listed
below may be taken as "most common practice", but they are
A. The 's suffix is preferred for one-syllable words (grass's) or
where the final syllable has a primary or secondary stress
B. The bare apostrophe is preferred:
- for words ending in -nce (stance');
- for many classical names (Aristophanes', Jesus', Moses');
- where the juxtaposition of two or more [s] sounds would
cause an awkwardness in pronunciation (thesis').
C. Usage is divided in the situation where the final [s] or [z]
sound falls in an unstressed syllable (octopus'/octopus's,
phoenix's/phoenix', and so on).
The question of which suffix is correct arises less often than
one might imagine. Instead of saying "the crisis' start" or "the
crisis's start", most native speakers of English would say "the
start of the crisis", thus avoiding the problem.
3. Plurals not ending in s: Use 's for the possessive plural
(men's, people's, sheep's).