Counter (typography)

In typography, a counter is the area of a letter that is entirely or partially enclosed by a letter form or a symbol (the counter-space/the hole of). The stroke that creates such a space is known as a "bowl". Latin letters containing closed counters include A, B, D, O, P, Q, R, a, b, d, e, g, o, p, and q. Latin letters containing open counters include c, f, h, s etc. The digits 0, 4, 6, 8, and 9 also have counters. An aperture is the opening between an open counter and the outside of the letter.