In typography

Typography

Typography is the art and technique of arranging type in order to make language visible. The arrangement of type involves the selection of typefaces, point size, line length, leading , adjusting the spaces between groups of letters and adjusting the space between pairs of letters...

, cap height refers to the height of a capital letter above the baseline

Baseline (typography)

In European and West Asian typography and penmanship, the baseline is the line upon which most letters "sit" and below which descenders extend.In the example to the right, the letter 'p' has a descender; the other letters sit on the baseline....

 for a particular typeface

Typeface

In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....

. It specifically refers to the height of capital letters that are flat—such as H or I—as opposed to round letters such as O, or pointed letters like A, both of which may display overshoot

Overshoot (typography)

In typeface design, the overshoot of a round or pointed letter is the degree to which it extends higher or lower than a comparably sized "flat" letter , to achieve an optical effect of being the same size....

. The height of the small letters is referred to as x-height

X-height

In typography, the x-height or corpus size refers to the distance between the baseline and the mean line in a typeface. Typically, this is the height of the letter x in the font , as well as the u, v, w, and z...

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