Apostrophe

The apostrophe (’, ') is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet and some other alphabets. In English, the apostrophe is used for two basic purposes:

• The marking of the omission of one or more letters, e.g., the contraction of "do not" to "don't"
• The marking of possessive case of nouns (as in "the eagle's feathers", "in one month's time", "the twins' coats")

It is also used in a few exceptional cases for the marking of plurals, e.g., "p's and q's" or Oakland A's. The same mark is used as a single quotation mark. It is also substituted informally for other marks – for example instead of the prime symbol to indicate the units of foot or minutes of arc. The word apostrophe comes from the Greek ἡ ἀπόστροφος [προσῳδία] (hē apóstrophos [prosōidía], '[the accent of] turning away or elision'), through Latin and French.

Usage in English

Historical development

The apostrophe was first used by Pietro Bembo in his edition of De Aetna (1496). It was introduced into English in the 16th century in imitation of French practice.

French practice

Introduced by Geoffroy Tory (1529), the apostrophe was used in place of a vowel letter to indicate elision (as in l'heure in place of la heure). It was also frequently used in place of a final ⟨e⟩ (which was still pronounced at the time) when it was elided before a vowel, as in un' heure. Modern French orthography has restored the spelling une heure.

Early English practice

From the 16th century, following French practice, the apostrophe was used when a vowel letter was omitted either because of incidental elision ("I'm" for "I am") or because the letter no longer represented a sound ("lov'd" for "loved"). English spelling retained many inflections that were not pronounced as syllables, notably verb endings ("-est", "-eth", "-es", "-ed") and the noun ending "-es", which marked either plurals or possessives, also known as genitives (see Possessive apostrophe, below). An apostrophe followed by ⟨s⟩ was often used to mark a plural; specifically, the Oxford Companion to the English Language notes:

There was formerly a respectable tradition (17th to 19th centuries) of using the apostrophe for noun plurals, especially in loanwords ending in a vowel (as in ... Comma's are used, Philip Luckcombe, 1771) and in the consonants s, z, ch, sh, (as in waltz's and cotillions, Washington Irving, 1804)...

Standardisation

The use of elision has continued to the present day, but significant changes have been made to the possessive and plural uses. By the 18th century, an apostrophe with the addition of an ⟨s⟩ was regularly used for all possessive singular forms, even when the letter ⟨e⟩ was not omitted (as in "the gate's height"). This was regarded as representing not the elision of the ⟨e⟩ in the "-e" or "-es" ending of the word being pluralized, but the elision of the ⟨e⟩ from the Old English genitive singular inflection "-es".

The plural genitive did not use the "-es" inflection, and since many plural forms already consisted of the "-s" or "-es" ending, using the apostrophe in place of the elisioned ⟨e⟩ could lead to singular and plural possessives of a given word having the exact same spelling. The solution was to use an apostrophe after the plural ⟨s⟩ (as in "girls' dresses"); however, this was not universally accepted until the mid-19th century. Plurals not ending in -s keep the -'s marker, such as "children's toys, the men's toilet", since there was no risk of ambiguity.

Possessive apostrophe

The apostrophe is used in English to indicate what is, for historical reasons, misleadingly called the possessive case in the English language. This case was called the genitive until the 18th century and, like the genitive case in other languages, expresses relationships other than possession. For example, in the expressions "the school's headmaster", "the men's department", and "tomorrow's weather", the school does not own/possess the headmaster, men do not own/possess the department, and tomorrow does not/will not own the weather. In the words of Merriam-Webster's Dictionary of English Usage:

The argument is a case of fooling oneself with one's own terminology. After the 18th-century grammarians began to refer to the genitive case as the possessive case, grammarians and other commentators got it into their heads that the only use of the case was to show possession ... Simply changing the name of the genitive does not change or eliminate any of its multiple functions.

That dictionary also cites a study, which found that only 40% of the possessive forms were used to indicate actual possession. The modern spelling convention distinguishes possessive singular forms ("Bernadette's", "flower's", "glass's", "one's") from simple plural forms ("Bernadettes", "flowers", "glasses", "ones"), and both of those from possessive plural forms ("Bernadettes'", "flowers'", "glasses'", "ones'"). For example, the word "glass's" is the singular possessive form of the noun "glass". The plural form of "glass" is "glasses" and the plural possessive form is, therefore, "glasses'". One would therefore say "I drank the glass's contents" to indicate drinking from one glass, but "I drank the glasses' contents" after also drinking from another glass. For singular forms, the modern possessive or genitive inflection is a survival from certain genitive inflections in Old English, for which the apostrophe originally marked the loss of the old ⟨e⟩ (for example, lambes became lamb's). Its use for indicating plural "possessive" forms was not standard before the middle of the 19th century.

General principles for the possessive apostrophe

Summary of rules for most situations

• Possessive personal pronouns, serving as either noun-equivalents or adjective-equivalents, do not use an apostrophe, even when they end in ⟨s⟩. The complete list of those ending in the letter ⟨s⟩ or the corresponding sound /s/ or /z/ but not taking an apostrophe is "ours", "yours", "his", "hers", "its", "theirs", and "whose".
• Other pronouns, singular nouns not ending in ⟨s⟩, and plural nouns not ending in ⟨s⟩ all take "'s" in the possessive: e.g., "someone's", "a cat's toys", "women's".
• Plural nouns already ending in ⟨s⟩ take only an apostrophe after the pre-existing ⟨s⟩ to form the possessive: e.g., "three cats' toys".

Basic rule (singular nouns)

For most singular nouns, the ending "'s" is added; e.g., "the cat's whiskers".

• If a singular noun ends with an ⟨s⟩-sound (spelled with "-s", "-se", for example), practice varies as to whether to add "'s" or the apostrophe alone. In many cases, both spoken and written forms differ between writers (see details below).
• Acronyms and initialisms used as nouns (CD, DVD, NATO, RADAR, etc.) follow the same rules as singular nouns: e.g., "the TV's picture quality".

Basic rule (plural nouns)

When the noun is a normal plural, with an added ⟨s⟩, no extra ⟨s⟩ is added in the possessive, and it is pronounced accordingly; so "the neighbours' garden" (there is more than one neighbour owning the garden) is standard rather than "the neighbours's garden".