[b.] Nouns ending in y preceded by a consonant (or by u as w) change the y to i and add es to form the plural.
- Examples: sky, skies; lady, ladies; colloquy, colloquies; soliloquy, soliloquies.
- Other nouns ending in y form the plural in the usual way. Examples: day, days; boy, boys; monkey, monkeys; valley, valleys.
[c.] Compound nouns usually form the plural by adding s or es to the principal word. Examples: sons-in-law, passers-by; but stand-bys, hat-boxes, writing-desks.
[d.] Letters, signs, and sometimes figures, add 's to form the plural. Examples: Cross your t's and dot your i's; ?'s; $'s; 3's or 3s.
[e.] A few nouns adhere to old declensions. Examples: ox, oxen; child, children; goose, geese; foot, feet; mouse, mice; man, men; woman, women; sheep, sheep; deer, deer; swine, swine.
[f.] Words adopted from foreign languages sometimes retain the foreign plural. Examples: alumnus, alumni; alumna, alumnæ; fungus, fungi; focus, foci; radius, radii; datum, data; medium, media; phenomenon, phenomena; stratum, strata; analysis, analyses; antithesis, antitheses; basis, bases; crisis, crises; oasis, oases; hypothesis, hypotheses; parenthesis, parentheses; thesis, theses; beau, beaux; tableau, tableaux; Mr., Messrs. (Messieurs); Mrs., Mmes. (Mesdames).
Exercise:
Write the singular and plural of the following words: day, sky, lady, wife, leaf, loaf, negro, potato, tomato, pass, glass, boat, beet, flash, crash, bead, box, passenger, messenger, son-in-law, Smith, Jones, jack-o'-lantern, hanger-on, stratum, datum, phenomenon, crisis, basis, thesis, analysis.
[Compounds]
[78a.] Use a hyphen between two or more words which serve as a single adjective before a noun: iron-bound bucket, well-kept lawn, twelve-inch main, normal-school teacher, up-to-date methods, twentieth-century ideas, devil-may-care expression, a twenty-dollar-a-week clerk.