_y_ preceded by a vowel (_a, e, i, o, u_) add
_s_; as, _valley, valleys_, (_soliloquy, soliloquies_ and _colloquy,
colloquies_ are exceptions). When _y_ is preceded by a consonant
(any letter other than a vowel), _y_ is changed to _i_ and _es_
is added; as, _army, armies; pony, ponies; sty, sties_.

4. Most nouns ending in _f_ or _fe_ add _s_, as, _scarf, scarfs;
safe, safes_. A few change _f_ or _fe_ to _v_ and add _es_; as,
_wife, wives; self, selves_. The others are: _beef, calf, elf,
half, leaf, loaf, sheaf, shelf, staff, thief, wharf, wolf, life_.
(_Wharf_ has also a plural, _wharfs_.)

5. Most nouns ending in _o_ add _s_; as, _cameo, cameos_. A number
of nouns ending in _o_ preceded by a consonant add _es_; as, _volcano,
volcanoes_. The most important of the latter class are: _buffalo,
cargo, calico, echo, embargo, flamingo, hero, motto, mulatto, negro,
potato, tomato, tornado, torpedo, veto_.

6. Letters, figures, characters, etc., add the apostrophe and _s_
(_'s_); as, _6's, c's, t's, that's_.

7. The following common words always form their plurals in an irregular
way; as, _man, men; ox, oxen; goose, geese; woman, women; foot,
feet; mouse, mice; child, children; tooth, teeth; louse, lice_.

COMPOUND NOUNS are those formed by the union of two words, either
two nouns or a noun joined to some descriptive word or phrase.

8. The principal noun of a compound noun, whether it precedes or
follows the descriptive part, is in most cases the noun that changes
in forming the plural; as, _mothers-in-law, knights-errant,
mouse-traps_. In a few compound words, both parts take a plural form;
as, _man-servant, men-servants; knight-templar, knights-templars_.

9. Proper names and titles generally form plurals in the same way
as do other nouns; as, _Senators Webster and Clay, the three Henrys_.
Abbreviations of titles are little used in the plural, except _Messrs._
(_Mr._), and _Drs._ (_Dr._).

10. In forming the plurals of proper names where a title is used,
either the title or the name may be put in the plural form. Sometimes
both are made plural; as, _Miss Brown, the Misses Brown, the Miss
Browns, the two Mrs. Browns_.

11. Some nouns are the same in both the singular and the plural;
as, _deer, series, means, gross_, etc.

12. Some nouns used in two senses have two plural forms. The most
important are the following:

BROTHER _brothers_ (by blood) _brethren_ (by association)
CLOTH _cloths_ (kinds of clot