In typography, emphasis is the strengthening of words in a text with a font in a different style from the rest of the text, to highlight them. It is the equivalent of prosody stress in speech.
Methods and use
The most common methods in Western typography fall under the general technique of emphasis through a change or modification of font: italics, boldface and . A means of emphasis that does not have much effect on blackness is the use of italics, where the text is written in a script style, or oblique, where the vertical orientation of each letter of the text is slanted to the left or right. With one or the other of these techniques (usually only one is available for any typeface), words can be highlighted without making them stand out much from the rest of the text (inconspicuous stressing). This is used for marking passages that have a different context, such as book titles, words from foreign languages, or internal dialogue.
By contrast, a bold font weight makes letters of a text thicker than the surrounding text. Bold strongly stands out from regular text, and is often used to highlight keywords important to the text's content. For example, printed dictionaries often use boldface for their keywords, and the names of entries can conventionally be marked in bold.
Small capitals () are also used for emphasis, especially for the first line of a section, sometimes accompanied by or instead of a drop cap, or for personal names as in bibliographies.
If the text body is typeset in a serif typeface, it is also possible to highlight words by setting them in a sans serif face. This practice is often considered archaic in Latin script, and on computers is complicated since fonts are no longer issued by foundries with a standard baseline, so switching font may distort line spacing. It is still possible using some font super families, which come with matching serif and sans-serif variants, though these are not generally supplied with modern computers as system fonts. In Japanese typography, due to the reduced legibility of heavier Minchō type, the practice remains common.
Of these methods, italics, small capitals and capitalization are oldest, with bold type and sans-serif typefaces not arriving until the nineteenth century.
Capitalization
The house styles of many publishers in the United States use all caps text for: chapter and section headings; newspaper headlines; publication titles; warning messages; and words of important meaning.
Capitalization is used much less frequently by British publishers, and usually only for book titles.
All-uppercase letters are a common substitute form of emphasis where the medium lacks support for boldface, such as old typewriters, plain-text email, SMS and other text-messaging systems.
Socially, the use of all-caps text in Roman languages has become an indicator of shouting when quoting speech. It was also often used in the past by American lawyers to flag important points in a legal text. Coinciding with the era of typewriter use, the practice became unnecessary with the advent of computerized text formatting, although it is still found on occasion in documents created by older lawyers.
Letter-spacing
Another means of emphasis is to increase the spacing between the letters, rather than making them darker, but still achieving a distinction in blackness. This results in an effect reverse to boldface: the emphasized text becomes lighter than its environment. This is often used in blackletter typesetting and typewriter manuscripts, but by no means restricted to those situations.
This letter-spacing is referred to as sperren in German, which could be translated as "spacing out": in typesetting with letters of lead, the spacing would be achieved by inserting additional non-printing slices of metal between the types, usually about an eighth of an em wide. On typewriters a full space was used between the letters of an emphasized word and also one before and one after the word.
For black letter type boldface was not feasible, since the letters were very dark in their standard format, and on (most) typewriters only a single type was available. Although letter-spacing was common, sometimes different typefaces (e.g. Schwabacher inside Fraktur), underlining or colored, usually red ink were used instead.