Glossary of Font & Type Terminology

This page contains a collection of useful type and font related terms, as defined by the team at Ascender.

ascender – The portion of lowercase letters which ascends above the x-height, as found in the letters b, d, f, h, k, l.

ascent – The vertical space above the baseline within which glyphs can be rendered without clipping.

baseline – The vertical origin upon which capital and non-descending lowercase letters sit.

bit depth – The number of bits used to define a color palette for bitmaps.

bitmap – An array of pixels which describe the shape of a glyph.

bowl – The round or elliptical portion of letters such as C, D, O, a, b, e, o and p.

cap height – The height of capital letters such as H, O and X.

character – The smallest component of written language which has semantic value.

character set – A list of characters, typically expressed as Unicode values, which defines the required character support for a font in a particular environment.

CJK – Chinese, Japanese and Korean. A common term to reference Asian scripts which use Han ideographs. Also: CJKV ('V' for Vietnamese).

clipping – The truncation of a glyph on one or more sides because its shape exceeds some font-wide metric.

code page – A defined set of characters typically associated with an operating system, and its locale. For example, CP1252 is the Windows Latin code page.

counter – The negative space within a letter, surrounded by positive elements such as stems, bowls and serifs.

descender – The portion of lowercase letters which descends below the baseline, as found in the letters g, j, p, q, y.

descent – The vertical space below the baseline within which glyphs can be rendered without clipping.

dingbat – A decorative pi character which is not a letter or mathematical symbol, but more likely a pictogram or icon. Common dingbats include decorative arrows, pointing hands, vehicles, etc,.

em – A measurement which is equal to the point size of a font. In the days of lead type this was typically a square within which the uppercase “M” of a text face was designed to fit. The ‘em square’ is thus the theoretical design space within which a typeface is typically drawn.

en – Half the size of an em.

encoding – A method of organizing a character set or glyph repertoire. See also code page.

fleuron – A pi character which is typically based upon or suggestive of flowers or leaves.

font – A collection of glyphs and other data which render a given typeface.

FreeType – An open source rasterizer which can support a variety of font formats, including bitmaps and OpenType fonts.

glyph – The graphical representation of one or more characters.

Han unification – An attempt by the Unicode Consortium to unify the character sets of Simplified Chinese, Traditional Chinese, Japanese and Korean scripts such that words of common origin share the same Unicode value, even though the shapes of those common words may differ between scripts.

hint – Any code or data which when interpreted by a font rasterizer will improve the resulting bitmap.

hinting – The process by which hints are developed for a font. Hints can be developed manually, automatically or a combination of the two. Automatically generated hints generally only provide modest improvements, whereas manual editing can allow for significant improvements at small sizes.

ideograph – A character which can symbolize whole words or concepts rather than just a sound. Ideographs are used in the Chinese, Japanese and Korean script systems.

kern – The adjustment of horizontal space between two glyphs. In metal type, the portion of a letter which hangs over the edge of the type body.

language – A system of communication which may include the use of scripts, speech or gestures.

leading – The vertical distance between lines of text. Historically this was expressed as points of lead (white space) inserted bewteen lines of text, such as 12 point type with 2 points leading, or "12 on 14". In digital type, the default leading of a font is determined by one of several different sets of values known as "vertical metrics".

ligature – Two or more characters represented on a single glyph. Common ligatures include “fi” and “fl”.

linegap – A vertical metric which adds white space between the bottom of the descent and the top of the following ascent.

lining figures – Numerals which have a common height, and thus align vertically with one another.

metrics – The generic term for any font or glyph measurements used in the setting of text. Horizontal metrics include advance widths, side bearings and kerning. Vertical metrics include ascent, descent and line gap dimensions.

metric compatibility – The concept of creating a font whose metrics may match an existing typeface for the purposes of preventing document reflow when changing fonts.

non-Latin – Scripts which are not Latin.

oldstyle figures – Numerals which vary in height such that 6, 8 and 9 ascend above the x-height and 3, 4, 5, 7 descend below the baseline.

OpenType – A scalable font format (ISO/IEC 14496-22) developed by Microsoft and Adobe, which brings together TrueType and Adobe’s CFF PostScript into a single standard, capable of rich and complex typography.

outline – One or more contours which describe the resolution-independent, idealized shape of a glyph.

pica – A typographical measurement equal to 12 points. There are 6 picas per inch.

pi character – Any generic or decorative glyph or symbol which is not properly associated with a specific typeface, but rather could be used with most any typeface.

pixel – A picture element. Previously thought to be the smallest controllable element on a screen or printer, this is no longer the case when considering ClearType™ or other sub-pixel rendering techniques.

point – A typographic unit of measure. 72 points = 1 inch.

point size – The size of a font measured in points.

PostScript – A page description language. The term “PostScript font” is commonly used to describe Adobe’s Type 1 font format, or CFF (Compressed Font Format).

ppem (Pixels Per Em) – The standard resolution-independent measure of type size.

rasterizer – The software component which interprets font data and renders text to the screen or printer.

resolution – The degree of precision capable for a given piece of hardware or software, generally expressed as a ratio of units per dimension. Examples include dpi (Dots Per Inch), ppem (Pixels Per EM) upem (font Units Per EM).

sans serif – A classification of typefaces which have no serifs.

scan converter – That portion of a rasterizer which converts the scaled and adjusted outline into pixels.

script – A set of graphical symbols and their rules for use to represent one or more languages.

serif – A flare or spur at the end of a stroke. A category of typefaces which exhibit serifs.

simplified Chinese – The standardized set of characters and shape of characters in use within mainland China. See also “traditional Chinese.”

sub-pixel – The smallest controllable element on a screen or printer. A typical RGB screen has each pixel made of 3 sub-pixels: red, blue & green.

swash – A decorative terminus on a glyph, generally applied to make the shape more elegant or florid.

symbol font – A pi font which typically uses a symbol encoding rather than a Unicode encoding.

tabular figures – Numerals which are all designed to the same width to facilitate setting of tabular matter, or columns of figures.

terminal – The name given to the end of strokes which have no serifs. Terminals generally fall into one of the following categories: ball, beak and teardrop.

traditional Chinese – The standardized set of characters and shape of characters in use within Hong Kong, Taiwan and Macau. See also “simplified Chinese.”

TrueType – A common font format invented by Apple Computer for their System 7.0 and adopted by Microsoft in Windows 3.1. TrueType is now a part of OpenType.

typeface – A collection of typographic characters (letters, numerals, punctuation, symbols) designed to be used together, and produced as one or more fonts.

Unicode – The Unicode standard is an encoding scheme (ISO/IEC 10646) used to uniquely identify characters, independent of language, region or code page.

x-height – The height of lowercase letters which do not ascend, such as n, o and x.