Of glyphs, type, typefaces, fonts, kerning, ligatures, etc.
Typography is the art of selecting particular forms for each letter and placing those selected glyphs on a surface in order to convey a set of words and a message. It is a dauntingly-large topic, one to which that many people devote their entire lives. It has long been my habit to spend a few hours each month looking into typography, exploring this field as a hobbyist.
Today I want to present some of the terminology in this field, at least as I understand it today. I may have some of it wrong; if so, I welcome corrections.
A character is a general term for letters, numbers, punctuation marks, and other typographic symbols. Characters are conceptual rather than graphical entities; “lower-case ‘a’” describes a character, while is a glyph.
A glyph is a visual structure used to present a character. Glyphs are graphical rather than conceptual entities, and a single typeface may contain multiple glyphs for a single character.
A ligature is a single glyph that represents two or more characters. They are commonly created because the respective glyphs for the individual characters do not look good in close proximity. The most common glyphs are “ff”, “fi”, and “fl”; an example is given in a three-glyph representation of the characters “fffii”: .
Incidentally, the ampersand character “&” was originally a ligature for “et”, the Latin word for “and.” If we still used “&” as a ligature we might write “g& m&ric ankl&s at the m&ropolitan mark&.” The character has since evolved until it is no longer suitable for use as a ligature.
A typeface is a collection of glyphs, typically including one glyph for each character in the local language in each of several different weights and forms.
A font is a process or tool for selecting and positioning glyphs from a particular typeface to represent a particular sequence of characters. It is possible to have many different fonts for a given typeface, each of which utilizes a different selection and placement process.
Typesetting is the entire process of turning conceptual content, in the form of a (possibly annotated) set of characters, into a visual presentation of glyphs on a surface.
In metal types, a kern was a portion of a glyph that protruded beyond the rectangular area the glyph occupied. They allowed letters to overlap horizontally. Kerning has since evolved into the process of selecting how to place adjacent glyphs within a single word. Kerning is often specified for pairs of characters; for example, in a well-kerned font “A” and “V” may be kerned to overlap horizontally.