Hyphens are used to link words and parts of words.
They are not as common today as they used to be, but there are three main cases where you should use them:
The rules about hyphens are not fixed. The points below are guidelines rather than rules.
Do not use a hyphen unless it serves a purpose. If a compound adjective cannot be misread or, as with many psychological terms, its meaning is established, a hyphen is not necessary.
- covert learning techniques
- health care reform
- day treatment program