A complete list of English prefix rules with examples and exceptions

Categories: Basic English

Prefix Rules in English

1. General Rule

Adding a prefix does not change the spelling of the base word.

• happy → unhappy

• kind → unkind

• appear → disappear

• possible → impossible

✅ Exception: With some prefixes, the final consonant in the prefix may change for easier pronunciation (assimilation).

2. Negative Prefixes

a. un- = “not / opposite of”

• happy → unhappy

• fair → unfair

• tidy → untidy

⚠️ Exceptions:

• Not used with some words where “in-” or “dis-” is preferred.

  • legal → illegal (NOT unlegal)

  • possible → impossible (NOT unpossible)

b. in- (and its variations) = “not”

• active → inactive

• correct → incorrect

• visible → invisible

• responsible → irresponsible

• legal → illegal

• mature → immature

???? Rule: in- changes spelling to match the first letter of the root word:

• il- before l (legal → illegal)

• im- before m, p (possible → impossible)

• ir- before r (regular → irregular)

c. dis- = “not, opposite of, reverse”

• agree → disagree

• appear → disappear

• connect → disconnect

• approve → disapprove

⚠️ Sometimes means “reverse the action”:

• tie → untie

• lock → unlock

• disarm → take away arms

d. non- = “not”

• sense → nonsense

• stop → nonstop

• fiction → nonfiction

✅ Used in formal/technical contexts (nonverbal, nonprofit).

3. Prefixes Showing Opposites or Reversal

• de- = reverse, remove → defrost, decode, deactivate

• anti- = against → antiwar, antibiotic

• counter- = opposite, against → counterattack, counterbalance

4. Prefixes of Degree/Size

• super- = above, extra → superhuman, supermarket

• over- = too much → overcook, overreact

• under- = not enough → underpaid, underdeveloped

• sub- = below → submarine, subway

• mini- = small → minibus, miniskirt

• micro- = tiny → microscope, microchip

• macro- = large → macrocosm, macroeconomics

5. Prefixes of Time/Order

• pre- = before → preview, prehistoric

• post- = after → postgraduate, postpone

• ex- = former → ex-president, ex-boss

• re- = again/back → rewrite, return, rebuild

⚠️ Exception: Words like remember, resist, repeat look like they have “re-” but they don’t mean “again”.

6. Prefixes for Place/Direction

• inter- = between → international, interact

• intra- = inside → intranet, intravenous

• trans- = across → transport, translate

• tele- = far → telephone, television

• sub- = under → subway, submarine

7. Prefixes for Number

• uni- = one → uniform, unicorn

• bi- = two → bicycle, bilingual

• tri- = three → triangle, tripod

• quadri- = four → quadrilateral

• multi- = many → multinational, multimedia

• poly- = many → polygon, polygamy

8. Spelling & Hyphen Rules with Prefixes

1. No hyphen needed usually

   • dislike, unhappy, reopen

2. Hyphen sometimes used

   • Before a capital letter → un-American, anti-Indian

   • To avoid double vowels/consonants → co-operate (BrE), co-own, re-enter

   • To avoid confusion → re-sign (sign again) vs resign (quit job)

3. Double letters

   • Usually allowed: unnatural, illogical

   • Sometimes dropped: cooperate (AmE, no hyphen)

✅ Summary

• Prefixes don’t change the root spelling (except assimilation in in-/im-/il-/ir-).

• Some words prefer specific negative prefixes (impossible, illegal).

• Hyphen rules apply when clarity or pronunciation is an issue.