Hyphens are used to divide or to compound words, word elements, or numbers
When do I use a hyphen to combine two words?
Use a hyphen to combine two words when modifying a noun
This three-inch heel = GOOD
This heel is three-inches = BAD
Infuse your wardrobe with urban-chic… = BAD
This urban-chic offering… = GOOD
EXCEPTION: adverbs ending in ly NEVER get a hyphen
Beautifully-crafted leather = BAD
Do I use a hyphen before a prefix?
Generally not, although the rule varies from word to word. When in doubt, visit m-w.com and look up the prefix (pre-, under-, etc.). Often you can find the correct usage of the word you are looking for in the word list under the prefix entry
What’s the difference between a hyphen and a dash?
There are three types of dashes:
Hyphen (or i-dash): looks like - and is used to compound words as above
En-dash: is the width of the letter "n" (–) and is used when omitting entries between two items, such as dates or amounts
For example: 1997–1998
Em-dash (or double hyphen): is the width of the letter "m" (—) and is used to interject information in a sentence
For example: A lot of people—doofuses, mostly—don’t know the differences between dashes.