- a letter of the alphabet that usually differs from its corresponding lowercase letter in form and height, as A, B, Q, and R as distinguished from a, b, q, and r: used as the initial letter of a proper name, the first word of a sentence, etc.
Word Origin and History for capital letters
late 14c.; see capital (adj.). So called because it is at the "head" of a sentence or word.
One of the two kinds of letters. Capital letters, also called upper-case letters, are larger than, and often formed differently from, lower-case letters. Capital letters are used at the beginning of a sentence or a proper name and may be used to show respect. Some examples are: “The dog barked,” Daniel, the Lord, and Queen Elizabeth.