Thomas Phinney’s glossary of typographic terms that document examiners (and others) may encounter or need to know in the course of their work.
This glossary page is licensed to others under cc-by 4.0.; credit Thomas Phinney / Font Detective LLC. (Yes, that means it is OK to include definitions from this in a forensic document report, with credit, and ideally a link.)
As a “live” document, definitions herein are subject to editing and revision. If you are a document examiner or an academic, needing an unchanging static version to reference, use the Internet Archive (Way Back Machine).
Some entries are placeholders for future content; this should be clear from the entry.
Feedback welcome!
- Advance Width: The width of a glyph in a font, including its left and right sidebearings. (The term literally means: how much to move forward when a glyph is set, before setting the next one.)
- Ascender: The height of vertical stems of lowercase letters, which in most fonts exceeds the cap height. Ascenders are seen in letters such as b d f h l.
- Typically the f overshoots the ascender height, while the t usually does not reach the ascender, although it still exceeds the x-height.
- Compare: descender.
- Baseline: The imaginary line that flat-bottomed glyphs (typically including A E L R T Z h n z 1 2 etcetera) rest their bottoms on. In western fonts, the baseline is at zero in the Y (vertical) dimension.
- Beard (1) or Spur: When the lower-right vertical element in a capital G extends below the semi-circular arc that it joins to, this is sometimes referred to as a beard.
- Beard (2): In metal type, this was also used to refer to the space between the baseline and the bottom of the type.
- Cap height: The height of flat-topped capital letters ,from the baseline (typically including E F H K T U V W X Y Z, and often D P R). This averages about 60–80% of the em and current point size.
- Note: If one is making a typeface, allowing for the needs of stacked diacritics for Vietnamese — as part of the initial design or for later potential additions — naturally leads toward smaller cap heights, in the low to middle of this range.
- Character: A character is something that has its own single codepoint in Unicode. For example, the capital A is a single character, but it is possible for a font to have more than one version of this character. Similarly, a font might combine several characters into one as a ligature.(Compare: glyph.)
- Chin: A feature present in some versions of a capital G, where there is a corner at the bottom right, where the outer round part of the G meets with a vertical element. For example, Aptos has no chin, whereas Helvetica and Arial do. (Compare: beard.)
- Condensed: See width.
- Contrast: The degree of difference between thick and thin strokes in a font. When they are of similar thickness, it is considered “low contrast”; when the thick strokes are dramatically heavier than the thin strokes, this is considered “high contrast.”
- This definition to be expanded with examples.
- Descender: The portion of a character that descends significantly below the baseline (that is, more than just overshoot), which in western-language fonts is typically an extension of an existing stroke. Letters that normally have descenders in western-language fonts include g j p q y (and if present, lowercase thorn: þ).
- Em or em square: The em is the internal scale in a digital font that is scaled to the current point or pixel size that you set a font at. For example, if you set a font at 12 point in print, it is the em that is scaled to 12 point, and everything else is relative to that. This is a bit counter-intuitive, because generally there is no single specific thing you can measure in the printed 12-point font, that is 12 points high.
- I wrote about point size and the em at great length in this 2011 blog post: https://www.thomasphinney.com/2011/03/point-size/
- Extended: See width.
- Font: in modern digital usage, a single computer file for a typeface. Most often, each style (regular, bold, italic, semibold, extra light, etcetera) is a separate font—although variable fonts can upend that concept. (In metal type, before photo and digital, a font was also limited to a specific size.)
- Glyph: A glyph is the contents of any single slot in a font. In most western fonts, most of the glyphs correspond 1-to-1 with Unicode characters. But this is by no means a requirement.
- For example, a font may have a single glyph that represents a sequence of two or more characters (e.g. a “Th” ligature, as seen in this very glossary), or multiple glyphs may be requiredto represent a single character (as is possible with combining marks base characters), or indeed, a single character may be represented by any of several different glyphs in a single font, as with a default capital A, a swash cap variant, a small cap variant, and a contextual variant that is only used when the next glyph is a period.
- Kerning: adjustments between specific glyph combinations. Usually it brings them closer together, where the shape combination might otherwise make them see too far apart. Some combinations that often need kerning adjustments include VA AV To LT.
- Although many programs allow users to adjust space between specific glyphs, kerning adjustments are often made by the designer of the font, and built into the font. It is up to programs using the font whether to enable these adjustments; some have kerning on by default, others allow it to be enabled.
- For a more detailed explanation, see: https://www.thomasphinney.com/2014/01/kerning-and-spacing-fonts/
Compare: Tracking.
- Ligature: A single glyph representing two or more characters. It may also be a character in its own right, but does not have to be. For example, many fonts (including my typeface used for this website) have an “fi” ligature. Most professional graphics programs have ligatures on by default; Microsoft Word only recently changed their defaults to have ligatures on by default.
- Monospaced: see width.
- Optical Size: Fonts may have design adjustments that tweak members of the same family to work better at larger or smaller sizes; these involve either separate fonts with distinct names for the different sizes, or a variable font with an “optical size” axis.
- When separate fonts are/were used, some of the names used to indicate different size variants have included: Micro, Caption, Small Text, Subhead, Display and Poster.
- Overshoot: Refers to both a concept and an amount, in type design. The concept is, that in order to appear the same height as the flat part of a letter, a round (or pointed) portion must be slightly higher (or lower, for bottom elements). The amount can depend on the circumstances, but is typically on the order of 1–3% for the top and bottom of a letter such as O/o, compared to a flat letter such as Z/z.
- Overshoot applies to elements such as the round parts of abdepqs and CGOS, the top of gnmr and the bottom of u. In some letters both the existence and amount of overshoot depends on the design, for example VW/vw get overshoot if their bottom elements are pointy, and not if they are flat and as wide as the bottom bits of H/h.
- Ascenders and descenders are separate concepts, but they too can have overshoot. Some letters generally have flat ascenders (or descenders) such as bdpq, while others typically have overshoot such as f and g.
- Point (unit): a unit of typographic measurement equal to 1/72 of an inch. When font size is measured in points, the size is not of any specific single part of a letter or glyph, but of the entire em square — the space the glyph is designed in. See: https://www.thomasphinney.com/2011/03/point-size/ for more details.
- On average, cap height for western fonts is around 60–80% of the point size, and the x-height is around 40–60%.
- Point (vector): when talking about vector font outlines, a point is a specific spot on a glyph contour whose coordinates are defined, at which is used in defining the glyph.
- Sidebearing: definition coming soon.
- Tracking: a constant glyph spacing adjustment, applied by the user or typesetter, to an entire range or block of text at once, making the glyphs all closer together or further apart.
Compare: Kerning - Spur: A small decorative projection from a main stroke, which unlike a serif, extends from a curve or angle.
- See also beard, which may be considered a special case of a spur.
- See also Tuscan.
- Tuscan: A style of type originating in 1800s wood type, in which most or all letters have decorative spurs.
- Typeface: the abstract design of a single set or family of related fonts.
- Variable Font: A technology that enables variation between styles of a font, with the styles and variation capability packaged as a single file (or at least fewer than normal, sometimes the upright and italic will be separate fonts, still). Specifically-enabled and labeled styles are called instances, and show up like separate fonts in an app font menu. But in apps that specifically support variable fonts, the user can also enable any in-between state, in apps that support it. For example, a font might have a weight axis, and have four or six or nine different pre-defined weights—but will also have the potential for any in-between value, in a “savvy̦” design app such as Adobe Illustrator or InDesign. A variable font family is often packaged as just one file (or sometimes two, if the italic is a separate font), as anything that varies continuously is handled within a single file.
See https://fonts.google.com/knowledge/introducing_type/introducing_variable_fonts
or https://www.axis-praxis.org/ - Weight: The degree of thickness of the strokes of glyphs in a font. Most of the time, this is expressed relatively. Although the average user is used to a typeface having only regular and bold for weights, typefaces may in fact have many further weights, including levels lighter than regular, in between regular and bold, and heavier than bold.
- More details coming soon.
- Width: (see also advance width.)
- Can refer to the width of a specific glyph or element in a glyph.
- More broadly, the overall or general width of the glyphs of a font. If the glyphs are narrower than average, it is most broadly referred to as condensed. If wider than average, it is most broadly referred to as extended. If all glyphs are on the same advance width, a font is referred to as monospaced.
- In modern digital fonts, there is a specific scale of possible widths, used by the font industry and sometimes on the web. Additionally, this scale may be used for variable fonts that choose to vary width. See the OpenType specification at https://learn.microsoft.com/en-us/typography/opentype/spec/os2#uswidthclass; table is reproduced just below this glossary.
- x-height: The height of the flat tops of lower-case letters such as x (and typically also u v w y z). Just a tiny bit less than letters that overshoot the x-height such as a e g m n o p q r s). Ascenders go far above the x-height, to cap height or beyond.
Width Values & Meaning
| Width Value | Description | % of normal |
|---|---|---|
| 1 | Ultra-condensed | 50 |
| 2 | Extra-condensed | 62.5 |
| 3 | Condensed | 75 |
| 4 | Semi-condensed | 87.5 |
| 5 | Medium (normal) | 100 |
| 6 | Semi-expanded | 112.5 |
| 7 | Expanded | 125 |
| 8 | Extra-expanded | 150 |
| 9 | Ultra-expanded | 200 |