2. Formation of the plural by internal change [goose, geese].
3. Fourteen nouns ending in f or fe change the f or fe into yes [leaf, leaves].
4. Nouns ending in y, preceded by a consonant, change the y to i and add es [enemy, enemies].
5. Letters, figures, signs, etc., form their plural by adding 's:[You have used too many i's].
6. Nouns taken from other languages usually form their plurals according to the laws of those languages [phenomenon, phenomena].
7. A few nouns in our language do not change their form to denote number.
(a) Some nouns have the same form, for both the singular and the
plural [sheep, deer].
(b) Some nouns are used only in the plural [scissors, thanks].
(c) Some nouns have no plurals [pride, flesh].
(d) Some nouns, plural in form, have a singular meaning [measles,
news, politics].
8. Compound nouns usually form their plural by pluralizing the noun part of the compound [sister-in-law, sisters-in-law]. If the words of the compound are both nouns, and are of equal importance, both are given a plural ending [manservant, menservants]. When the compound is thought of as a whole, the last part only is made plural [spoonful, spoonfuls].
9. Proper names usually form their plurals regularly. If they are preceded by titles, they form their plurals either by pluralizing the title or by pluralizing the name [The Misses Hunter or the Miss Hunters. The Messrs. Keene or the two Mr. Keenes. The Masters Burke. The Mrs. Harrisons.]
10. A few nouns have two plurals differing in meaning or use [cloth, cloths, clothes; penny, pennies, pence].
+24. Case.+—Case is the relation that a noun or pronoun bears to some other word in the sentence.