Paratype Typographic Glossary

x-height

The distance between the Baseline and the Midline of an alphabet, which is normally the approximate height of the unextended Lowercase letters – a, c, e, m, n, o, r, s, u, v, w, x, z – and of the torso of b, d, h, k, p, q, y. The relation of x-height to Cap height, and the relation of x-height to length of extenders, are two important characteristics Latin typeface.
See picture.

x-line

See Mean line.