Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021
Capitalize proper nouns and words derived from them; do not capitalize common nouns
Capitalization
Mechanics
Proper nouns are the names of specific persons, places, and things. All other nouns are common nouns. The following types of words are usually capitalized: names of deities, religions, religious followers, sacred books; words of family relationship used as names; particular places; nationalities and their languages, races, tribes; departments, degrees, particular courses at educational institutions; government departments, organizations, political parties; historical movements, periods, events, documents; and trade names. The next page lists examples of proper and common nouns.
PROPER NOUNS |
COMMON NOUNS |
✵ God (used as a name) |
✵ a god |
✵ Uncle Pedro |
✵ my uncle |
✵ Father (used as a name) |
✵ my father |
✵ the South |
✵ a southern state |
✵ Environmental Protection Agency |
✵ a federal agency |
✵ the Democratic Party |
✵ a political party |
✵ the Enlightenment |
✵ the eighteenth century |
✵ the Treaty of Versailles |
✵ a treaty |
✵ Advil |
✵ a painkiller |
Months, holidays, and days of the week are treated as proper nouns: May, Memorial Day, Monday. The seasons and numbers of the days of the month are not: summer, the seventh of September.
EXCEPTION: Capitalize Fourth of July (or July Fourth) when referring to the holiday.
Names of school subjects are capitalized only if they are names of languages: English, Mandarin. Names of particular courses are capitalized: Geology 101.
The term Internet is typically capitalized, but other common nouns related to the Internet and computers are not: home page, website. Usage varies widely, however, so check the rules of the discipline or style in which you are writing.