Sheet 07Revised 19 Aug 2026

Typography glossary: the terms that carry a decision

Roughly seventy terms cover almost everything said about type in practice. They are grouped below by what they describe rather than alphabetically, because the grouping is itself the lesson: the terms that name parts of a letter behave very differently from the terms that name space between letters.

A long wooden index-card box seen from above, full of blank cards and taller divider tabs, one violet.

No. 331A glossary is a card box. The dividers matter more than the cards, which is why this one is grouped.

The letterform

Glyph: One drawn shape in a font. A character is what a reader means; a glyph is what a font draws. One character can have several glyphs, and one glyph can serve several characters.
Stem: The main vertical stroke, and the reference weight the rest of the letter is drawn against.
Bowl: The closed curve of b, d, o, p, q.
Counter: The enclosed space inside a bowl. First thing to close up when a face is set too small.
Aperture: The opening of a nearly-closed letter such as c, e, s. The strongest predictor of legibility at small size.
Serif: The finishing stroke at the end of a stem. Wedge, slab or hairline, bracketed or not.
Bracket: The curve joining serif to stem. Present in old-style faces, absent in Didones, and the fastest single test for telling the two apart.
Terminal: How a stroke ends where there is no serif: flat, angled, or a ball.
Spur, ear, tail, leg, link: The small identifying features that separate one revival of a historical face from another.
Axis: The angle through the thinnest points of a lowercase o. Angled means the letter descends from a pen; vertical means from an engraver or a compass.
Contrast: The ratio of thinnest to thickest stroke. Near 1:1 in a grotesque, beyond 1:6 in a Didone.
Overshoot: The tiny amount a round letter extends past a line so that it does not appear to float above it.

Lines and heights

Baseline: The line the letters sit on.
x-height: The height of the lowercase x. What a reader perceives as the size of a face.
Cap height: The height of the capitals.
Ascender: The part of b, d, h, k, l rising above the x-height.
Descender: The part of g, j, p, q, y falling below the baseline.
Em: A relative unit equal to the current type size. The square the design is drawn inside.
En: Half an em. The width of the en dash, which is the correct dash for a range.
Point: One seventy-second of an inch in digital type. A measure of the em square, not of any visible part of the letter, which is why two faces at the same point size look different sizes.

Space

Sidebearing: The space designed into the left and right of a glyph. Belongs to the font.
Kerning: A pair-specific adjustment stored in the font (AV, To, Ye) applied automatically.
Tracking: A uniform adjustment across a run, applied by whoever is setting the type. Also called letter-spacing.
Leading: The distance from one baseline to the next. Named after the strips of lead once inserted between lines of metal type.
Word space: The space between words. Fixed in ragged setting, elastic in justified setting, which is where rivers come from.
Measure: The length of a line, usually counted in characters. Roughly 45 to 75 characters is the working range for continuous prose.

Setting a paragraph

Justified: Both edges flush, achieved by stretching and compressing word spaces. Needs hyphenation to avoid rivers, and needs a measure long enough to absorb the adjustment.
Ragged right: Left edge flush, right edge uneven. Word spaces stay constant, so the texture is even at any measure.
River: A vertical channel of white running down a justified paragraph where word spaces happen to line up. The reason justification without hyphenation is a mistake.
Widow: A short last line of a paragraph stranded at the top of a column.
Orphan: A first line of a paragraph stranded at the bottom of one.
Hyphenation: Breaking a word across lines by a language's own rules. The mandatory partner of justified setting.
Indent: The first-line step that marks a new paragraph. An alternative to a blank line, not an addition to it: using both marks the same thing twice.
Hanging punctuation: Pushing quotation marks and hyphens slightly outside the measure so the edge of the column reads as straight.

Families and weights

Family: All the related faces sharing a design: weights, widths, italics.
Weight: The thickness of the stroke, from thin to black. Numbered 100 to 900 on the web.
Width: How compressed or extended the design is. A real condensed cut is drawn; a squashed one is a distortion and looks it.
Italic: A separate cursive drawing, not a slanted roman.
Oblique: A slanted roman, drawn deliberately as such. Common in grotesques.
Optical size: A cut drawn for a specific size range: heavier and more open for small text, finer and tighter for display.
Variable font: One file carrying continuous axes (weight, width, optical size) so that any instance along them can be rendered. Usually smaller than three static weights.
Small capitals: Capitals drawn at roughly x-height with their own weight. Scaled-down real capitals are not the same thing and read as too light.
Lining and old-style figures: Lining figures all stand at cap height; old-style figures have ascenders and descenders and sit better inside running prose.
Tabular and proportional figures: Tabular figures all share one width so columns align. Proportional figures are spaced individually and read better in a sentence.

Files and production

OpenType: The current font format, carrying the outlines plus features such as kerning, ligatures and figure sets.
WOFF2: The compressed web font format. Compression is Brotli, and the saving over the raw file is substantial.
Subsetting: Cutting a font down to the characters actually used. This site subsets nine display faces to only the glyphs each one sets, which keeps every one of them under three kilobytes.
Unicode range: A declaration telling the browser which characters a font file covers, so it is only downloaded when one of them appears.
Font display: The rule deciding what a browser shows while a web font is loading. Swap shows the fallback immediately, which trades a visible substitution for never showing nothing.
Hinting: Instructions telling a rasteriser how to fit outlines to a pixel grid. Much less important than it was, and still not nothing at small sizes.
Reserved font name: A name an open licence protects. A modified version must be renamed, which is the single most broken condition in open font licensing.

Where a term above changes a decision rather than merely naming a thing, it has its own entry on this reference: the letterform parts, the family names, the licence terms and the spacing controls are each worked through in full.

Questions about the vocabulary

Queries

What is the difference between kerning and tracking?

Kerning is a pair-specific adjustment stored inside the font and applied automatically: the closing of AV or To. Tracking is a uniform adjustment applied across a whole run by whoever is setting the type. Kerning belongs to the designer of the font; tracking belongs to you.

What is a good line length for body text?

Between roughly 45 and 75 characters including spaces, with about 66 as a common target. Shorter forces too many returns; longer makes it hard for the eye to find the start of the next line, which is why long measures need more leading to stay readable.

Are italics just slanted letters?

No. A true italic is a separate cursive drawing with different letterforms: the single-storey a is the clearest tell. A slanted roman is called an oblique, and it is a deliberate design choice in grotesques rather than a substitute for an italic.

Why does the same point size look bigger in one font than another?

Because the point size measures the em square the design sits inside, not any visible part of the letter. What the eye reads as size is the x-height, and that varies widely: by more than eight percentage points of the cap height across the three faces this site sets its text in.