In typography, the breaking of a word into syllables and inserting hyphens, manually or automatically, so that word spaces remain consistent—within prescribed limits—for proper justification.
There are several basic rules for hyphenation:
1. There must be at least two characters on both sides of the hyphen.
2. Numerals should not be hyphenated except, in an emergency, at a comma point.
3. It is not good practice to hyphenate in a headline.
4. A one-syllable word should never be hyphenated, though some systems will certainly try.
5. A word should be divided on a double consonant, unless the word root ends with a double consonant (e.g., miss-ing, not mis-sing).
6. More than three hyphens should not be used in a row. Too many hyphens in a row (or too many hyphens in a text block) is referred to as pig bristles.
An incorrect word division is called a bad break. For maximum legibility, hyphenation should be used as little as possible.
A discretionary hyphen is inserted in a word during input to give the system a specific point to hyphenate, and that point will take precedence over any logic-generated point. Often, a DH at the beginning of a word tells the system not to hyphenate the word at all.
Logic hyphenation refers to a system where the computer is programmed with certain logical rules for hyphenating words at the ends of lines. However, no program is infallible. Hence, the need for an "exception dictionary," a collection of the program's incorrectly hyphenated words held in the computer's memory. With luck, the system will search the exception dictionary before consulting the logic program.
Hyphenation is often considered together with justification, forming a joint concept called hyphenation and justification.