In word processing, hyphenation refers to splitting a word that would otherwise extend beyond the right margin. Not all word processors support hyphenation, and of those that do support it, not all perform it correctly.
Word processors use two basic techniques to perform hyphenation. The first employs an internal dictionary of words that indicates where hyphens may be inserted. The second uses a set of logical formulas to make hyphenation decisions. The dictionary method is more accurate but is usually slower. The most sophisticated programs use a combination of both methods.
Most word processors allow you to override their own hyphenation rules and define yourself where a word should be divided.