Aperture (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). Letters containing closed counters include A, B, D, O, P, Q, R, a, b, d, e, g, o, p, and q. Letters containing open counters include c, f, h, i, s etc. The digits 0, 4, 6, 8, and 9 also possess a counter. An aperture is the opening between an open counter and the outside of the letter.

The lowercase 'g' has two typographic variants: the single-story '' has one closed counter and one open counter (and hence one aperture); the double-story '' has two closed counters.

The digit 4 also has two typographic variants: the closed-top variant '' has a closed counter, and an open-top (e.g. handwritten) '' has an open counter.

Different typeface styles have different tendencies to use open or more closed apertures. This design decision is particularly important for sans-serif typefaces, which can have very wide strokes making the apertures very narrow indeed.

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