It’s easy to become confused over the proper use of the humble hyphen. The main purpose of which is to join two (or more) words together, thereby making them a single compound word with its own meaning. As in:
• an ex-President is a former President.
• a co-director works with another director.
The absence of a hyphen can also lead to misunderstanding:
• I must re-cover the sofa (with new material).
• I must recover the sofa (from the person I lent it to).
• After his time in prison, he was a reformed character (no longer a criminal).
• They re-formed the band and played in the garage (started up again).
Prefixes like co- and pre- should have a hyphen when next to a word beginning with the same vowel, as in: co-ordinate, pre-empt.
Hyphens can contribute considerably to clarity, as in:
You must read two hundred odd pages a day which gives the impression you are only to read the odd pages, hence the hyphen in: You must read two hundred-odd pages a day.
There are several word combinations which are hyphenated when they come before a noun, but not when they come after, as in these examples.
He is a well-known author.
This author is well known.
She is a part-time worker.
She works part time.
It’s all as clear as mud, I hear you say. Ah, don’t you just love the English language.