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).
- "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
- the test was self-paced
Exception: self psychology
Words that could be misunderstood
- re-pair [pair again]
- re-form [form again]
Words in which the prefix ends and the base word begins with the same vowel
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-centered counseling
the counseling was client centered
- t-test results
results from t tests
- same-sex children
children of the same sex
General Principle 4
Write most words formed with prefixes and suffixes as one word.
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
See the Publication Manual for exceptions to these principles.
(adapted from the sixth edition of the APA Publication Manual, © 2010)