For most writers, the hyphen’s primary function is the formation of certain compound terms. The hyphen is also used for word division, which is briefly explained here.
Compound terms are those that consist of more than one word but represent a single item or idea. They come in three styles.
Open (or spaced) compounds are written as separate words.
chief of staff
The en dash (–) is slightly wider than the hyphen (-) but narrower than the em dash (—). The typical computer keyboard lacks a dedicated key for the en dash, though most word processors provide a means for its insertion.
Span or range of numbers
The en dash is used to represent a span or range of numbers, dates, or time. There should be no space between the en dash and the adjacent material. Depending on the context, the en dash is read as “to” or “through.”
Notwithstanding its versatility, the em dash is best limited to two appearances per sentence. Otherwise, confusion rather than clarity is likely to result.