The value of anatomical vocabulary is diagnostic. Without it, a wrong letter can only be described as looking wrong; with it, the fault can be located — the aperture is too closed, the terminal is cut at the wrong angle, the joint is too thick where the shoulder meets the stem. Every term below names a part that can be measured, compared and corrected.
The horizontal reference lines
Five imaginary horizontals organise every alphabet.
- Baseline
- The line the letters sit on. It is the one absolute reference; almost every other measurement is taken from it.
- x-height
- The height of a lowercase x, and by extension the height of the main body of the lowercase. The ratio of x-height to cap height is the single most consequential proportion in a typeface: a large x-height makes text look bigger at the same nominal size and improves small-size identification, at the cost of shortening the extenders that give words their distinctive outline.
- Cap height
- The height of the capitals. In most text faces capitals stop slightly below the ascenders, which prevents an initial capital from looking oversized next to a following lowercase l or h.
- Ascender line
- The top of letters such as b, d, f, h, k and l.
- Descender line
- The bottom of g, j, p, q and y. Descender depth is the main variable determining how tightly lines can be set before collisions begin.
These lines are not obeyed exactly. Round letters and pointed letters must overshoot the line they meet, typically by around one per cent of the cap height, because a curve or a point touching a flat reference at a single tangent point appears smaller than a flat-topped letter that meets it along its whole width. A geometrically exact O looks short beside a geometrically exact H. Overshoot corrects an error in perception, not in the drawing.
Strokes and their parts
- Stem — the main upright of a letter, and the element whose weight defines the whole alphabet's colour.
- Bowl — the closed curved stroke enclosing space, as in b, p, o and the lower half of a.
- Counter — the enclosed or partly enclosed space itself. The counter is a drawn shape in its own right; drawing it as an afterthought is the commonest structural fault in amateur letterforms.
- Shoulder — the curved stroke leaving a stem and returning to the baseline, as in h, m and n.
- Arm and leg — horizontal or diagonal strokes attached at one end only; an arm rises or projects, a leg descends.
- Crossbar — the horizontal joining two strokes, as in A and H. In an f or t the equivalent horizontal crossing a stem is a cross stroke.
- Spine — the central curve of an S, and the hardest single stroke to draw well, since its two curves must balance without either dominating.
- Apex and vertex — the junctions where two diagonals meet at the top and bottom respectively, as at the top of A and the bottom of V.
- Spur, ear and tail — small projections: the spur on a G, the ear on a lowercase g, the tail on a Q or R.
Aperture, terminals and stress
Aperture is the width of the opening where a counter connects to the surrounding space — the gap in a c, the mouth of an e or an a. Open apertures keep letters distinguishable at small sizes and under poor reproduction, because they preserve the difference between a c and an o, or an e and an a, even when ink spread or antialiasing thickens every stroke. Closed apertures read as formal and compact and fail first at small sizes. This is one of the most reliable predictors of how a face will behave under adverse conditions, and it matters directly for the thresholds discussed under legibility.
Terminals are the ends of strokes that carry no serif. They may be cut flat and horizontal, cut on an angle, rounded, tapered, or finished with a ball or teardrop. Terminal treatment is a strong period marker: flat horizontal cuts read as rational and modern, angled cuts as calligraphic, ball terminals as nineteenth-century. The classification these signals map onto is set out in the serif field guide.
Stress is the axis along which a round letter is thinnest. Draw a line through the two thinnest points of an O: if it is vertical, the stress is vertical or rational; if it tilts, the stress is oblique or humanist. Oblique stress is a fossil of the broad-edge pen, whose fixed angle necessarily thins the stroke along a diagonal — the mechanism described under hand lettering. Vertical stress had to be invented deliberately, because no pen produces it naturally.
Contrast, weight and width
Stroke contrast is the ratio of the thickest stroke to the thinnest. A monoline face has a ratio near 1:1; a high-contrast didone may exceed 10:1. Contrast is the main reason a face looks robust or fragile, and it interacts badly with scale: high-contrast letters set small lose their hairlines to ink spread or screen rendering, while low-contrast letters set very large look inert.
Weight and width are separate axes that are frequently confused. Weight is stroke thickness relative to the letter's size; width is the horizontal proportion of the letter relative to its height. Adding weight without adding width closes counters, which is why heavy display faces are normally drawn wider — the interaction described under logotype design. In variable font formats, weight and width are exposed as independent axes precisely because they cannot be derived from one another.
Using the vocabulary
A drawn letter is best judged by isolating one system at a time: first the skeleton, then the weight distribution, then the counters as positive shapes, then the terminals. Faults that appear inexplicable when the letter is viewed as a whole usually resolve immediately when the counter is examined alone. Standard definitions of these terms, cross-referenced and illustrated, are published in the Google Fonts glossary, and a condensed set specific to this site is kept in the glossary. Original drawings and specimen material showing how these decisions were made historically are held by collections such as the Letterform Archive, while the technical documentation of contemporary weight and width axes is published by foundries including Monotype.