Font is an aspect that only applies to text. A font is all the letters, numerals, and punctuation marks of one typeface size. This means, for example, that Helvetica 12-point and Helvetica 14-point are different fonts. Roman fonts are also distinct from italic fonts. (In the era of digital composition, these difference are often elided.)

Fonts can be categorized multiple ways: serif or sans-serif, old style or modern, monospaced or proportional, text or display, print or screen, etc. Each font also has multiple characteristics, such as its x-height and cap-height. Because of these variations, fonts are exceptionally flexible and potent, so font choices should always seek to further a document's rhetorical goals.

Font choices are the basis of a document's typography, and are a primary way of establishing a document's consistency and creating meaningful instances of contrast.