In typography, emphasis usually refers to means of stressing parts of a text by using letters in a different style from the rest of the text to make them stand out from the main text body.
Methods and uses of emphasis
Fig. 1: Roman emphasis example
The human eye is very receptive to differences in brightness within a text body. One can therefore differentiate between types of emphasis according to whether the emphasis changes the "blackness" of text.
A means of emphasis that does not have much effect on "blackness" is printing in italics, where the text is written in a script style, or oblique , where the vertical orientation of all letters is slanted to the left or right. With one or other of these techniques (usually only one is available for any typeface), words can be highlighted without making them "stick out" much from the rest of the text (inconspicuous stressing). Traditionally, this is used for marking passages that have a different context, such as words from foreign languages, book titles, etc.
By contrast, boldface makes text darker than the surrounding text. With this technique, the emphasized text strongly stands out from the rest; it should therefore be used to highlight certain keywords that are important to the subject of the text, for easy visual scanning of text. For example, printed dictionaries often use boldface for their keywords; Wikipedia follows this convention when the name of each article is marked at the top in bold.
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 is somewhat of an archaic practice.
Emphasis in design
With both italics and boldface, the emphasis is correctly achieved by temporarily replacing the current typeface. Professional typographic systems (which include most modern computers) would therefore not simply tilt letters to the right to achieve italics (that is instead referred to as slanting) or print them darker for boldface, but instead use entirely different typefaces that achieve the effect. As can be seen in Fig. 1, the "w" letter, for example, looks quite different in italics compared to the regular typeface.
As a result, typefaces therefore have to be supplied at least fourfold (with computer systems, usually as four font files): as regular, italics, bold, and both bold and italics to provide for all combinations. Professional typefaces sometimes offer even more variations for popular fonts, with varying degrees of blackness. Only if such fonts are not available should the effect of italics or boldface be imitated by tilting or blacking the original font.
Alternative methods for emphasis
Fig. 2: blackletter emphasis example
In Germany, a different means of emphasis was previously used. To achieve a variance in blackness, instead of making the letters darker, one would increase the spacing between them. This resulted in an effect reverse to boldface: the emphasized text becomes lighter than its environment. This was referred to as sperren in German ("letterspacing" in English), which could here be translated as "spacing out". While sperren normally means "to lock (out)", this particular meaning was figurative: with the older method of typesetting with letters of lead, the spacing would be achieved by inserting additional non-printing slices of metal between the types.
The example text reads: "An example of German text in Fraktur in which a portion of the text is spaced out. It is noticed, as with boldface, clearly as opposed to the rest of the text.
The reason for this particular German typographic convention can be seen in the traditional use of blackletter typefaces, for which boldface was not feasible, since the letters were very dark in their standard format. The blackletter typefaces were officially abolished in 1942 by Nazi Germany, and after that, its use quickly diminished. As a result, the use of spacing as a means of emphasis in printed materials quickly became obsolete. However, spacing is sometimes still used as a means of emphasis in typographic media where only one typeset is available, e.g. in typewritten communication or on text-only computer terminals.
Special punctuation marks
In Chinese, emphasis in body text is supposed to be indicated by using an "emphasis mark" (着重號), which is a dot placed under each character to be emphasized. This is still taught in schools, but in practice it is not usually done, probably due to the difficulty of doing this in most computer software. Methods used for emphasis in western texts but inappropriate for Chinese, for example underlining and setting text in artificially slanted type (frequently incorrectly called "italics"), are often used instead.