A typographic hierarchy expresses the organization of content, emphasizing some elements and subordinating others. A visual hierarchy helps readers scan a text, knowing where to enter and exit and how to pick and choose among its offerings. Each level of the hierarchy should be signaled by one or more cues, applied consistently across a body of text. A cue can be spatial (indent, line spacing, placement) or graphic (size, style, color). Infinite variations are possible.
Writers are trained to avoid redundancy as seen in the expressions “future plans” or “past history.” In typography, some redundancy is acceptable, even recommended. For example, paragraphs are traditionally marked with a line break and an indent, a redundancy that has proven quite practical, as each signal provides backup for the other. To create an elegant economy of signals, try using no more than three cues for each level or break in a document.
Emphasizing a word or phrase within a body of text usually requires only one signal. Italic is the standard form of emphasis. There are many alternatives, however, including boldface, small caps, or a change in color. A full-range type family such as Scala has many weight and style variations designed to work together. You can also create emphasis with a different font. If you want to mix font families, such as Scala and Helvetica, adjust the sizes so that the x-heights align.