Hyphens: prefixes and punctuation

Hyphens with Prefixes

Rule 1

The current trend is to do away with unnecessary hyphens. Therefore, attach most prefixes and suffixes onto root words without a hyphen.

Examples:
noncompliance
copayment
semiconscious
fortyish

Rule 2:

Hyphenate prefixes when they come before proper nouns.

Example: 
un-American

Rule 3

Hyphenate prefixes ending in an a or i only when the root word begins with the same letter.

Examples:
ultra-ambitious 
semi-invalid

Rule 4

When a prefix ends in one vowel and a root word begins with a different vowel, generally attach them without a hyphen.

When the prefix ends in one vowel and a root word begins with a consonant, write a hyphen, e.g.,  anti-crisis  ( the Daily Telegraph) 

Examples: 
antiaircraft
proactive

Rule 5

Prefixes and root words that result in double e's and double o's are usually combined to form one word.

Examples:
preemployment
coordinate

Exceptions:
de-emphasize
co-owner

Rule 6

Hyphenate all words beginning with self except for selfish and selfless.

Examples:
self-assured
self-respect
self-addressed

Rule 7

Use a hyphen with the prefix ex.

Example:
His ex-wife sued for nonsupport.

Rule 8

Use the hyphen with the prefix re only when:

the re means again AND omitting the hyphen would cause confusion with another word.

Examples:
Will she recover from her illness?
Re does not mean again.

I have re-covered the sofa twice.
Re does mean again AND omitting the hyphen would have caused confusion with another word.

The stamps have been reissued.
Re means again but would not cause confusion with another word.

I must re-press the shirt.
Re means again AND omitting the hyphen would have caused confusion with another word.