Prefixes & Suffixes

Intermediate · Word Formation

You can multiply your vocabulary quickly by understanding word parts. A prefix goes at the START of a word and usually changes its meaning (happy → unhappy). A suffix goes at the END and often changes the word class (happy → happiness, a noun).

Learn the common building blocks and you can understand and create thousands of words.

How to build it

prefix + root (changes meaning) · root + suffix (changes word class)

Rules & examples

  1. Negative prefixes: un-, in-, im-, il-, ir-, dis-, mis-.

    They reverse the meaning. The choice often depends on the first letter of the root.

    • happy → unhappy
    • possible → impossible
    • legal → illegal
    • agree → disagree
  2. Other useful prefixes: re- (again), pre- (before), over- (too much), under- (too little).

    They add a specific idea.

    • redo, preview, overcook, underpay
  3. Noun suffixes: -tion, -ment, -ness, -ity, -er/-or.

    They turn verbs/adjectives into nouns.

    • inform → information
    • happy → happiness
    • teach → teacher
  4. Adjective suffixes: -ful, -less, -able, -ive, -ous.

    They turn nouns/verbs into adjectives.

    • care → careful/careless
    • enjoy → enjoyable
    • danger → dangerous
  5. Adverb suffix: -ly turns an adjective into an adverb.

    The most common word-building step of all.

    • quick → quickly
    • happy → happily

Tips to remember

  • im- before m/p (impossible, immature); il- before l (illegal); ir- before r (irregular); in- for many others (incorrect).
  • -ful (full of) vs -less (without): careful vs careless, hopeful vs hopeless.

Common mistakes

  • ✗ unpossible → ✓ impossible — The correct negative prefix here is "im-", not "un-".