Prefixes

A prefix is a group of letters added to the start of a word to change its meaning: ⟦happy → unhappy⟧, ⟦write → rewrite⟧. The spelling of the word itself never changes, so ⟦un-⟧ + ⟦necessary⟧ keeps both ⟦n⟧s: ⟦unnecessary⟧. Knowing what a prefix means helps you work out new words.

Key facts

  • ⟦un-⟧, ⟦dis-⟧, ⟦in-⟧ mean not or the opposite: ⟦unkind⟧, ⟦disagree⟧, ⟦incorrect⟧. Before a verb ⟦un-⟧ can mean undo: ⟦unlock⟧, ⟦unpack⟧.
  • ⟦im-⟧ goes before ⟦m⟧ and ⟦p⟧ (⟦impossible⟧, ⟦immature⟧), ⟦il-⟧ before ⟦l⟧ (⟦illegal⟧), ⟦ir-⟧ before ⟦r⟧ (⟦irregular⟧). All mean not.
  • ⟦re-⟧ means again: ⟦rebuild⟧, ⟦reread⟧, ⟦refill⟧.
  • ⟦mis-⟧ means wrongly: ⟦misspell⟧, ⟦misunderstand⟧, ⟦misbehave⟧.
  • ⟦pre-⟧ means before: ⟦preview⟧, ⟦preheat⟧, ⟦prehistoric⟧.
  • Keep every letter: ⟦mis- + spell = misspell⟧, ⟦il- + legal = illegal⟧, ⟦ir- + regular = irregular⟧.

Worked examples

Example 1

Make the opposite of ⟦polite⟧ with a prefix.

  1. ⟦polite⟧ starts with ⟦p⟧.
  2. Before ⟦m⟧ or ⟦p⟧ the prefix for not is ⟦im-⟧.
  3. ⟦im- + polite = impolite⟧

Answer: ⟦impolite⟧

Example 2

What does ⟦rewrite⟧ mean?

  1. The prefix is ⟦re-⟧, which means again.
  2. The root word is ⟦write⟧.
  3. So ⟦rewrite⟧ means to write again.

Answer: to write again

Example 3

Add ⟦mis-⟧ to ⟦spell⟧.

  1. The prefix ends in ⟦s⟧ and the word starts with ⟦s⟧.
  2. Neither part changes, so there are two ⟦s⟧s: ⟦misspell⟧.

Answer: ⟦misspell⟧

Example 4

Choose: ⟦unlegal⟧, ⟦inlegal⟧ or ⟦illegal⟧?

  1. ⟦legal⟧ starts with ⟦l⟧.
  2. Before ⟦l⟧ we use ⟦il-⟧: ⟦illegal⟧.

Answer: ⟦illegal⟧