Which Words Are Not Capitalized in a Title?

Three kinds of word stay lowercase in the middle of a title: articles, prepositions and coordinating conjunctions. Every style guide agrees on the first and the last. The fight is over prepositions, and the answer depends on which guide you follow.

Always lowercase (in the middle)

Articles: a, an, the.

Coordinating conjunctions: and, but, or, nor, for, and in most guides so and yet.

The word "to" before a verb: How to Cook, What to Expect. Chicago and MLA say this explicitly; APA and AP reach the same result because to is two letters.

Every one of these is capitalized when it is the first word of the title, and all of the guides used on this site capitalize the last word too. The Road Not Taken. What Are We Waiting For.

Prepositions: the four-letter line

Short prepositions are lowercase everywhere: at, by, in, of, on, to, up. The guides split on longer ones.

APA and AP use a length rule. A preposition of four letters or more is capitalized: With, From, Into, Over, Between, Through. A preposition of three letters or fewer stays lowercase.

Chicago and MLA use a part-of-speech rule. A preposition is lowercase whatever its length: with, from, between, underneath. Only when a preposition is doing a different job does it get a capital, which is the next section.

So the same title comes out two ways:

• APA: Living With Diabetes: Lessons From Thirty Years of Practice
• Chicago: Living with Diabetes: Lessons from Thirty Years of Practice

Neither is wrong. If you are not sure which your reader expects, the APA version is the more common one on the web, and the Chicago version is the more common one in published books. The title case converter shows both side by side if you switch the style tab.

When a "small" word is not small

Part of speech is decided by use, not by spelling. The same three letters can be a preposition in one title and something else in the next.

Phrasal verbs. In Turn Off the Lights, off is part of the verb turn off, and Chicago capitalizes it: Turn Off. In Fell off the Ladder it is a plain preposition and stays small. Most people get this wrong in the same direction, lowercasing Up in Look Up and Set Up. Not every guide makes this distinction, and the converter on this site keeps the simpler rule of treating off and up as prepositions, so check phrasal verbs by hand if you are following Chicago closely.

"As". Chicago lowercases as in every role. APA lowercases it because it is short. Both come out the same: Teaching as Performance.

"Is", "Are", "Be", "Am". These are verbs. They are capitalized in every guide, even though they are short. Why Sleep Is Not Optional. The length rule in APA and AP was never meant to touch verbs.

"That", "This", "It", "Its". Pronouns and determiners, so capitalized: The House That Jack Built, Why It Matters.

Subordinating conjunctions. Because, Although, If, When, Unless are not coordinating conjunctions, and Chicago and MLA capitalize them. APA capitalizes the long ones by the length rule and lowercases if as a short conjunction. The one real disagreement here is If: capital in Chicago and MLA, lowercase in APA.

After a colon

The first word after a colon is always capitalized, even if it is a or the. Second Chances: A Study of Re-Entry Programs. This also applies after a dash used to introduce a subtitle, and after a question mark inside the title.

A table you can keep

Words that stay lowercase in the middle of a title, by guide:

• APA 7: a, an, the, and, as, but, for, if, nor, or, so, yet, at, by, in, of, off, on, per, to, up, via. Anything with four or more letters gets a capital.
• AP: a, an, the and any preposition or conjunction of three letters or fewer. Verbs are always capitalized.
• Chicago 18: a, an, the, and, but, for, or, nor, as, to (as infinitive marker), and every preposition regardless of length.
• MLA 9: the same list as Chicago, and like Chicago it capitalizes subordinating conjunctions such as Because and If.

The quickest way to be right

Do not memorise the lists. Decide which guide the reader expects, paste the title into the capitalization tool, select that guide and copy the result. Then check two things by eye: any phrasal verb (set up, log in, turn off) and any name that has its own capitals, such as iPhone or eBay. The tool keeps brand names intact, but it cannot know whether your off is a verb particle or a preposition. That is the only judgement call left.