Affixes — Opposites of Words (Primary English, Age 11)

An affix is a small part added to a word to change its meaning. When we add some affixes we make the opposite of a word. This note looks at common prefixes and one suffix that make opposites.

Common affixes that make opposites

  • un- — means "not" or the opposite. (happy → unhappy)
  • in- / im- / il- / ir- — all forms of the prefix in-. They mean "not" or "opposite". The form changes to fit the first letter of the root:
    • im- before b, p, m (possible → impossible)
    • il- before l (legal → illegal)
    • ir- before r (regular → irregular)
  • dis- — often means the opposite or "not" especially with verbs and some adjectives (agree → disagree)
  • non- — means "not" or "without" (fiction → nonfiction)
  • mis- — often means "wrong" or "badly" (behave → misbehave). This does not always give the opposite.
  • -less (suffix) — added to nouns or adjectives to mean "without" (hope → hopeless)

Examples (base → opposite)

happyunhappy
meaning: not happy
sentence: She felt unhappy about the lost book.
possibleimpossible
meaning: not possible
sentence: It was impossible to finish in five minutes.
legalillegal
meaning: not legal
sentence: Stealing is illegal.
agreedisagree
meaning: have the opposite opinion
sentence: I disagree with that idea.
fictionnonfiction
meaning: not fiction (real facts)
sentence: This book is nonfiction.
hopehopeless
meaning: without hope
sentence: Their situation looked hopeless.

Spelling tips

  • Most prefixes are added without changing the root: kind → unkind.
  • The prefix in- changes to im-, il-, or ir- to make the word easier to pronounce: possible → impossible; legible → illegible; regular → irregular.
  • The suffix -less is added directly: use → useless; hope → hopeless.
  • Some prefixes like mis- mean "wrong" not always the exact opposite. Check the meaning in a dictionary if unsure.

Quick practice

  1. Add a prefix to make the opposite: tidy → _______
  2. Choose the correct form of in-: polite → _______ (use il-/im-/ir- if needed)
  3. Fill in the blank with a word using a negative affix: He was ________ (able).
  4. Change to opposite using a prefix: honest → _______
  5. Use suffix -less: power → _______
Answers
  1. untidy
  2. impolite (im- before p)
  3. unable
  4. dishonest
  5. powerless

Final tip: When you see a word with an extra small part at the start or end, ask: "Does this change the meaning to 'not' or 'without'?" If yes, it is probably a negative affix forming an opposite.

➖ ➕ = Opposite

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