A manual for writers of research papers, theses, and dissertations, Ninth edition - Kate L. Turabian 2018

Possessives
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20.2.1 General Rule

Form the possessive of most singular common and proper nouns, including those that end in s, x, or z, by adding an apostrophe and s. This rule also applies to letters and numerals used as singular nouns, and to abbreviations. It also applies to proper names ending in s (whether or not the s is pronounced), as in the last three examples. (Do not confuse possessives with plural forms, which are described in 20.1.) For special cases, see 20.2.2.

✵ an argument’s effects

✵ the horse’s mouth

✵ 2018’s economic outlook

✵ the phalanx’s advance

✵ the waltz’s tempo

✵ JFK’s speech

✵ Russ’s suggestion

✵ Descartes’s Discourse on Method

✵ Aristophanes’s plays

Inanimate nouns—except for references to time—rarely take the possessive form.

Form the possessive of most plural common and proper nouns by adding only an apostrophe. For special cases, see 20.2.2.

For irregular plurals that do not end in s, add s after the apostrophe.

✵ the mice’s nest

✵ children’s literature

20.2.2 Special Cases

20.2.2.1 SINGULAR NOUNS ENDING IN “S.” Form the possessive of the following types of nouns with only an apostrophe:

✵ ▪ nouns that name a group or collective entity but are treated as grammatically singular

o politics’ true meaning

o the United States’ role

✵ ▪ nouns in a few traditional For . . . sake expressions that end in an s or an s sound

o for goodness’ sake

o for righteousness’ sake

but

o for appearance’s sake

To avoid an awkward result, rephrasing is sometimes the better option. (For use of the abbreviation US in a case like the first one below, see 24.3.1.)

20.2.2.2 COMPOUND WORDS. Form the possessives of singular compound words by adding an apostrophe and s to the last word, even if the main noun is first.

✵ his sister-in-law’s business

✵ the attorney general’s decision

Form the possessives of plural compounds in the usual way (by adding an apostrophe alone), unless the plural part comes first (see 20.1.2). In that case, rephrase.

✵ district attorneys’ decisions

but

✵ decisions of the attorneys general

not

✵ attorneys’ general decisions

and not

✵ attorneys general’s decisions

20.2.2.3 MULTIPLE NOUNS. If a possessive indicates that two or more entities each possess something separately, make all the nouns possessive.

✵ New York’s and Chicago’s teams

✵ historians’ and economists’ methods

If a possessive indicates that two or more entities possess something jointly, make only the last noun possessive.

✵ Minneapolis and St. Paul’s teams

✵ historians and economists’ data

20.2.2.4 TERMS IN ITALICS AND QUOTATION MARKS. If a term in italics is possessive, both the apostrophe and the s should be in roman type. Do not add a possessive to a term in quotation marks; rephrase the sentence.

✵ the Atlantic Monthly’s editor

✵ admirers of “Ode on a Grecian Urn”

If the term ends in a plural form, add only an apostrophe (in roman type). If it already ends in a possessive form, leave it alone or rephrase.

✵ the New York Times’ online revenue

✵ Harper’s editors (or the editors of Harper’s)