A-manual-for-writers-of-research-papers-theses-and-dissertations

suggested here.20.1 Plurals20.1.1 General RuleFor most common nouns, form the plural by adding s (or es, for words ending in ch, j, s, sh, x,or z). Most dictionaries give plural forms only for words that do not follow the general rule.The general rule applies to the names of persons and to other proper nouns, includingNative American tribes. If such a noun ends in y, do not change the y to ie, as required forcommon nouns. (Do not confuse plural forms with possessives, which are described in 20.2).the Costellosthe Frys (not the Fries)the Rodriguezesthe two Germanysthe Hopis of Arizona (not the Hopi)20.1.2 Special CasesCOMPOUND WORDS. For compound words consisting of two nouns, add s or es to the lastnoun.bookkeepersdistrict attorneysactor-singersWhen a prepositional phrase or adjective follows, add s or es to the main noun.sisters-in-lawattorneys generalmen-of-warLETTERS AND NUMERALS. In most cases, form the plurals of capital letters and numerals byadding s alone (not 's).the three Rsthe 1950s767sWith lowercase letters and some single capital letters, however, an s without an apostrophecan seem to create a different word (is, As) or an abbreviation (ms). If the s might createconfusion, add an apostrophe. The apostrophe and s are roman even if the letter is italic (see22.2.2).dotting all the i'sx's and y'sthree A's and two B's