Hyphens
When do you need to use a hyphen for compound words?
General Principle 1
If a compound adjective can be misread, use a hyphen.
General Principle 2
In a temporary compound that is used as an adjective before a noun, use a hyphen if the term can be misread or if the term expresses a single thought (i.e., all words together modify the noun).
For example:
"the adolescents resided in two parent homes" means that two homes served as residences, whereas if the adolescents resided in "two-parent homes," they each would live in a household headed by two parents.
A properly placed hyphen helps the reader understand the intended meaning.
Also use hyphens for
Compounds in which the base word is
capitalized: pro-Freudian
a number: post-1970
an abbreviation: pre-UCS trial
more than one word: non-achievement-oriented students
All "self-" compounds whether they are adjectives or nouns
self-report
self-esteem
the test was self-paced
Words that could be misunderstood
re-pair [pair again]
re-form [form again]
un-ionized
Words in which the prefix ends and the base word begins with the same vowel
meta-analysis
anti-intellectual
co-occur
General Principle 3
Most compound adjective rules are applicable only when the compound adjective precedes the term it modifies. If a compound adjective follows the term, do not use a hyphen, because relationships are sufficiently clear without one.
client-centred counselling but the counselling was client centred
t-test results but results from t tests
same-sex children but children of the same sex
General Principle 4
Write most words formed with prefixes and suffixes as one word.
Prefixes
aftereffect
extracurricular
multiphase
socioeconomic
Suffixes
agoraphobia
wavelike
cardiogram
General Principle 5
When two or more compound modifiers have a common base, this base is sometimes omitted in all except the last modifier, but the hyphens are retained.
Long- and short-term memory
2-, 3-, and 10-min trials
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