Hyphenation is the name for the act — and the system — of joining words or breaking them with a hyphen. When a teacher talks about hyphenation, they mean the rules: where the dash goes, and which word-pairs get one. In printing and on a computer, hyphenation also means breaking a long word at the end of a line so the page looks neat. Different dictionaries, and British and American publishers, do not always choose the same breaks. Though actually, a lot of modern writing just avoids hyphenation and lets the whole word jump to the next line. The word names the practice, not the little dash itself.