Capitalization is a complex issue, with many rules and exceptions.
This post outlines the basic, most common guidelines for capitalization, with examples.
Academic degrees: Lowercase—”bachelor’s degree”; capitalize entirety of most abbreviations (with a few exceptions, including PhD and DLitt)
Academic disciplines: Capitalize only proper names—”Asian studies” (except as part of a full name of an entity (“the School of Business,” “the Department of Philosophy,” “the Commission on the Liberal Arts,” etc.)
Acronyms and initialisms: Capitalize most abbreviations of proper names—NATO, FBI (but some style guides and writing handbooks call for using initial capitalization only for extensive and established acronyms, as with Nasdaq); most abbreviations for units of measurement are not capitalized, but check a dictionary or style guide for exceptions
Animal names: Lowercase terms except in the case of proper names—”African elephant,” “Steller’s jay” (do the same for animal breeds, as in “Labrador retriever,” though specialized publications often capitalize all words in breed names); capitalize first word in binomial and trinomial nomenclature (” Homo sapiens,” “Gorilla gorilla gorilla“), but differentiate between nomenclature and popular name (“Pinus ponderosa,” but “ponderosa pine”)
Astronomical terms: Capitalize most names of specific bodies and collections of bodies—”the Milky Way,” but “the solar system”; capitalize Earth (and Moon and Sun) in astronomical references but lowercase in terrestrial or figurative contexts—”The third planet is Earth,” but “The earth is flat” (do not capitalize earth when the word is preceded by the) and “Where on earth is he?” (and “The sun is about to rise” and “The moon is full”)
Brand names and trademarks: Follow capitalization as used by the brand owner, but ignore logo format—for example, the brand names Lego and Time (the magazine) are treated as all-caps in the respective company logos; companies discourage genericization of trademarks such as kleenex and xerox, but writers have no obligation to honor such usage as “Kleenex Brand Facial Tissue”
Color terms for ethnic identification: Lowercase unless a company or publication prefers otherwise—”black man,” “white people”
Compass points: Generally lowercase, but capitalize in geopolitical contexts—”the Pacific Northwest,” “customs prevalent in the East”)
Cultural terms: Look up specific terms, as treatment varies widely—”art deco,” but Beaux-Arts
Emphasis: Capitalize only in ironic contexts—”He was apparently a Big Man on Campus”; do not capitalize entire words, except perhaps to denote a newspaper headline or signage (and then, small caps are recommended)
Epithets: Capitalize key words—”Alfred the Great,” “Babe Ruth,” “Michael ‘Air’ Jordan,” “the Windy City,” “Big Pharma”
File formats: The Chicago Manual of Style recommends capitalizing names of formats, but do so only in such usage as “I made a GIF from the video,” and lowercase (and precede with a dot) in references to files such as “The latest version of Microsoft Word uses the file extension .docx”
Foreign terms: German capitalizes all nouns, but lowercase German words adopted into English—hausfrau, schadenfreude, weltanschauung (if it’s in the dictionary, it’s English)
Geographical names: Capitalize in proper names, but lowercase in generic usage—”the Mississippi River,” but “the river”; check style guides for variations such as “the Pacific coast”/”the West Coast”; lowercase metaphorical and nonliteral use of proper names—”manila envelope,” “They set out to create a utopia”
Historical terms: Look up specific terms, as treatment varies widely—”the colonial period,” but “the Gilded Age”
Honorifics: Capitalize key words—”Her Majesty,” “Your Honor” (but “Yes, my lord”)
Key commands: Capitalize words denoting switch, keyboard, and command functions—”the Pause button,” “the Command key,” “the Save command,” etc.
Kinship names: Capitalize only in direct address or in place of or in combination with a name—”Yes, Mother,” “We’re going to Grandmother’s house,” “Uncle Joe” (but “my uncle Joe”)
Laws, theories, and the like: Capitalize only proper names—”Newton’s third law,” “the Pythagorean theorem”
Letters as letters: Capitalize only if the letter is specified as an uppercase letter—”a capital C” (exception: letter grades, as in “She earned four A’s”)
Letters as shapes or musical notes, or points, concepts, or hypothetical names: Capitalize—”a V-shaped symbol,” “from point A to point B,” etc. (exception, lowercase—but italicize—letters in rhyming schemes, as in “an abab pattern”)
Medical conditions: Capitalize only proper names—”Alzheimer’s disease,” but “muscular dystrophy”
Natural events and phenomena : Capitalize names of storms but otherwise lowercase generic words—”Hurricane Harvey,” but “the San Francisco earthquake”
Organizational entities: Capitalize in proper names, but lowercase in generic usage—”the Federal Bureau of Investigation,” but “the bureau”—and “the federal government”); lowercase generic versions of entity names—”the company,” “the museum,” “the committee,” etc.; lowercase the preceding entities’ names (unless house style allows exceptions)
People’s names: Capitalize names of real and fictional people, but lowercase figurative usage—”Jack Nicholson,” “Jack Sprat,” but “every man jack”; capitalize personifications—”Mother Nature,” “Ol’ Man River”
Prefixes for proper names: Look up specific terms, as treatment varies—pre-Columbian, but transatlantic
Seasons: Lowercase—winter, spring, summer, fall
Titles of compositions: Capitalize key words—”Pride and Prejudice” (check a style guide for specifics)
Titles of jobs and offices: Capitalize key words before the name (except when modified) and lowercase after the name or in isolation—”Director of Marketing John Smith,” “Pastor Jane Jones” (but “former director of marketing John Smith,” “John Smith, director of marketing,” and “the director of marketing,” as well as “the pastor”); capitalize in direct address (“As you were, Sergeant”) or in formal written contexts or in a ceremonial or promotional list
Titles of nobility: Capitalize before names and when using full title in isolation—”There’s Prince Charles,” “the Duke of Windsor” (but “the duke”)
A version of this post first appeared on Daily Writing Tips.