The Editor's Manual
Free learning resource on English grammar, punctuation, usage, and style.
Avoid capitalizing corporate job titles when used descriptively or as common nouns. Capitalize them when used as part of a name or to address a person.
Capitalize words like “professor” and “principal” as titles before a name, but not when used descriptively after a name or as common nouns.
Capitalize words like “king,” “prince,” “duke,” and “duchess” when used in titles or before a name (“King Charles III, son of Queen Elizabeth II and Prince Philip, Duke of Edinburgh”). References to a specific person may also be capitalized (“the King”).
Words like “pope,” “bishop,” “rabbi,” “reverend,” and “father” are capitalized as religious titles before a name but lowercased as common nouns.
Capitalize kinship titles (mom, dad, uncle, grandma, etc.) when using them as names (“Hi, Mom”), but lowercase them as common nouns (“your mom”).
Capitalize military ranks like “general” and “captain” when used as titles before a name or to address a person. Lowercase them as common nouns.
Capitalize names of people, places, companies, departments, and geographical features. Whether a word is capitalized depends upon whether it is being used as a proper noun or simply as a common noun. In titles and headings, capitalize the first and last words and all other words except articles, prepositions, and conjunctions.
Capitalize words like “sir” and “madam” in a salutation (“Dear Sir or Madam”) and when used before a name or as a title (Sir Sean Connery, Madam President). Otherwise, they are generally lowercased (“Yes, ma’am”).
In headings and book or movie titles, capitalize the first word, last word, and all other words except articles, prepositions, coordinating conjunctions, and the word “to.” Various style guides prescribe additional rules.
Form the plural of an acronym or other abbreviation simply by adding an “s” (URLs, DVDs). No apostrophe is needed. Abbreviated SI units do not have a separate plural form (1 cm and 10 cm).