As we discussed in Hyphen Help, there are specific rules for using hyphens with words. And the dictionary is your friend.

This week, I’m going to cover the rules of hyphens with one word. Should you use a hyphen or combine the prefix and root word? It depends.

Common terms used in this post:

Prefix = comes at the front of a word (two to four letters)

Suffix = comes at the end of a word (two to four letters)

Proper noun = A particular person (being) or thing, capitalized

Vowel = a, e, i, o, u, sometimes y

Root word = a word within a word that has a prefix or suffix

* Most times it is okay not to use a hyphen. If in doubt, look it up or go without. The following rules are when to use a hyphen with a word:

1. Use a hyphen when a prefix comes before a proper noun. As you can see combining them would look a little odd because the proper noun is capitalized.

Examples: un-American, non-Baptist

2. Use a hyphen if a prefix ends in a or i and the root word begins with the same letter.

Examples: semi-intoxicated, ultra ambitious

3. Hyphenate all words that begin with self. The only exceptions are selfish and selfless.

Examples: self-addressed, self-supporting

4. If the prefix is -ex, use a hyphen.

Examples: ex-husband, ex-Marine

5. If the prefix is re-, only use a hyphen when re- means again and not using a hyphen would create another word.

Examples: re-sort vs. resort; re-creation vs. recreation; re-covered vs. recovered

When to not use a hyphen and just combine the parts to create word:

1. When a prefix ends in one vowel and a root word begins with a different one, combine them.

Examples: antiaircraft, coauthor, preamble

2. If you get a double e or double o, combine the parts. However there are exceptions, so be sure to look it up if you are not sure.

Examples: cooperative, proactive

Exceptions: co-owner, de-emphasize

(The only reason I could see these being exceptions is because they would look odd without the hyphen. If you know the rule, or have another opinion, I’d love to hear it!)

Sources: The Blue Book of Punctuation and Grammar, merriamwebster.com, my brain