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

This page reflects guidance from the sixth edition of the Publication Manual.

For the most current guidelines, see the Publication Manual of the American Psychological Association (7th ed.) and our Style and Grammar Guidelines page for the seventh edition.

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

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)