When to Use a Capital Letter at the Start of a Sentence
(Including after Colons and in Quotations)

The Quick Answer
Use a capital letter at the start of a sentence. (This includes sentences within quotation marks.)

The words following a colon do not usually start with a capital letter, unless the introduction is short and the words after the colon are the main idea and a complete sentence.

A Capital Letter to Start a Sentence

Start every new sentence with a capital letter. This seems like a fairly simple ruling, but there are some quirks.

Capital Letters after Colons, Dashes, or Semicolons

When a sentence is divided by a dash, a semicolon, or a colon, you will often have two "sentences" either side of it. In fact, these are not two sentences but two independent clauses. Only the first one (i.e., the one that starts the sentence) gets a capital letter. For example:
  • In this world there are only two tragedies: one is not getting what one wants, and the other is getting it. (Oscar Wilde)
  • (Note: No capital letter on one.)
However, with a colon, if the introduction is short and the words which follow the colon are the main idea and a standalone sentence, then it is possible to use a capital letter for style purposes. For example:
  • Our motto: Live every day to the fullest – in moderation. (Lindsay Lohan)
There is a lot of leniency on this. If you feel a capital letter is right, use it. If you think it looks awkward, go for a lowercase letter.

Of course, if the first word should have a capital letter in its own right (e.g., it's a proper noun (e.g., London, George Harrison, Wal-Mart) or an abbreviation (e.g., CNN, BBC, Nato)), then obviously it keeps its capital letter.

Capital Letters within Quotation Marks

If your sentence contains a quotation which is a standalone sentence, start the quotation with a capital letter. For example:
  • At 4 o'clock, he stood up and said: "You can all leave if you wish."
  • (In this example, the quote is a standalone sentence. Therefore, it gets a capital letter.)
  • He was considered "the sexiest man ever to come out of Barnsley."
  • (Here, the quote is a not a standalone sentence.)
There is another consideration. If the original version of "the sexiest man ever to come out of Barnsley" started with a capital letter, then a capital T could have been used in the last example above. There is a lot of leniency on the use of capital letters for quotations embedded in sentences. You are safe to let your desired flow of text and how your sentence looks determine whether to use a capital or lowercase letter.

See Also

Capital letters in advertisements Capital letters and the points of the compass Using capital letters with proper and common nouns Capital letters with the four seasons What is title case? Test on using capital letters