Okay, I have a headache from reading all the rules on when to use hyphens LOL And I'm still confused at times. Holy Confusing Mix of Contradicting Rules, Grammar Man!
However, I found a wonderful site with tons of good info and lots of examples of all these confusing rules. So, thanks to The Grammar Curmudgeon, Rich Turner (please check out his site for all your grammar needs, he has TONS of good stuff over there - the info and most of the examples listed below come from his site), here's what I found out.
1. Use hyphens for numbers - twenty-eight; two-thirds, etc
2. Use a hyphen when you are using two or more adjectives that act as a single idea -
low-budget job (the job is not low and budget, it is low-budget)
well-known author (though after the noun you wouldn't use it...the author is well known)
go-ahead (She gave me the go-ahead on the project)
- In other words, if you can add a comma or "and" and keep the meaning, you probably don't need a hyphen. For example:
The red, ripe apple fell from the tree.
You wouldn't say red-ripe apple because the apple is both red and ripe, two separate descriptions that work independently from each other.
3. When prefixed by ex-, self-, all-
And occasionally cross-
4. When needed for clarity -
You need to re-sign the forms to resign your position.
We studied the re-creation process for recreation.
5. When the second word is capitalized -
6. Other examples -
Another interesting fact that I sort of knew but never really thought about -
Words evolve. They tend to start out as two words, then get hyphenated and eventually end up as one word....like database.
For more examples (and rules....and explanations of those rules) check out The Grammar Curmudgeon's site. He's got more info over there then you ever wanted to know :D