[ 'hʌɪf(ə)n ]
■ noun the sign (-) used to join words to indicate that they have a combined meaning or that they are grammatically linked, or to indicate word division at the end of a line.
Origin
C17: via late L. from Gk huphen 'together'.
Usage
In modern English the use of ~s is in general decreasing, especially in compound nouns: website is preferred to web-site , and air raid to air-raid . Hyphens are still often employed to clarify meaning where a compound expression precedes a noun, as in twenty-odd people . When a phrasal verb such as build up is made into a noun it is usually ~ated ( a build-up of pressure ). However, a normal phrasal verb should not be ~ated: write continue to build up your pension not continue to build-up your pension .