Prefixes
Elementary School
Definition
A word part added to the beginning of a base word to change its meaning. For example, adding "un-" to "happy" makes "unhappy," meaning not happy. Knowing common prefixes helps readers work out the meanings of unfamiliar words.
Worked examples
"The teacher asked us to rewrite our essays."
The prefix 're-' means 'again,' so rewrite means to write again.
"She was unhappy about the misunderstanding."
'Un-' means 'not' (not happy) and 'mis-' means 'wrongly' (wrongly understood).
Common mistakes
- thinking 'in' always means 'not' (e.g., 'inside' means 'not side') → 'in' can mean 'not' (incorrect) or 'into' (inside) — check the base word The same prefix can have different meanings depending on context.
- breaking 'interest' as 'inter-' + 'est' to find meaning → 'interest' is not built from a prefix — not every word has one Only break apart words where the prefix and base are both real word parts.
- thinking 'pre-' in 'pretty' means 'before' → 'pretty' has no prefix — it's a complete base word Not every letter group at the start is a prefix; the rest must be a meaningful base.
Where you'll use it next
Understanding prefixes helps you decode advanced vocabulary in reading comprehension, write precisely by choosing the right modifiers, and tackle SAT/ACT vocabulary questions confidently.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026