When do you need to use a hyphen for compound words?

General Principle 1

Do not use a hyphen unless it serves a purpose. If a compound adjective cannot be misread or, as with many psychological terms, its meaning is established, a hyphen is not necessary.

For example

  • covert learning techniques
  • health care reform
  • day treatment program
  • sex role differences
  • grade point average

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

Exception: self psychology

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-centered counseling
    but
    the counseling was client centered
  • 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

See the Publication Manual for exceptions to these principles.

(adapted from the sixth edition of the APA Publication Manual, © 2010)