5.1.3.3 Capitalization of Titles in English

In English titles, use headline-style capitalization. Capitalize the first and last words of the title and subtitle, as well as nouns, pronouns, verbs, adjectives, adverbs, and subordinating conjunctions. Lowercase articles, coordinating conjunctions, and prepositions, regardless of length, unless they appear as the first or last word of the title or subtitle.

Hyphenated compounds should usually capitalize the first element. Capitalize later elements when they are major words, but lowercase articles, coordinating conjunctions, and prepositions unless they function adverbially. When a hyphen follows a prefix rather than a complete word, capitalize the following element only if it is a proper noun or proper adjective.

For more detailed rules and examples, see CMS17, §8.157–161.