Prefixes & Their Meanings

In this lesson, you will learn about prefixes — small groups of letters added to the beginning of a word to change its meaning. Understanding prefixes is like having a secret code-breaker for the 11+ exam. Even if you see an unfamiliar word, knowing its prefix can help you work out what it means.

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What Is a Prefix?

A prefix is a group of letters placed at the start of a word to create a new word with a different meaning.

Example:

• happy → unhappy (not happy)
• view → preview (to see before)
• do → redo (to do again)

The prefix changes the meaning, but the original word (the root word) stays the same.

Key Rule: When you add a prefix, you do NOT change the spelling of the root word. Simply attach the prefix to the front.

• mis + spell = misspell (not "mispell")
• un + necessary = unnecessary (not "unnecesary")
• dis + satisfy = dissatisfy (not "disatisfy")

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Common Prefixes and Their Meanings

Study this table carefully. These are the prefixes you are most likely to encounter in the 11+ exam.

Prefixes That Mean "Not" or "Opposite"

Prefix	Meaning	Example words
un-	Not; opposite of	unhappy, unkind, unfair, unusual, uncertain
dis-	Not; opposite of; apart	disagree, disappear, disconnect, dislike, dishonest
in-	Not	invisible, incorrect, incomplete, independent, inadequate
im-	Not (before m, p, b)	impossible, impatient, immature, impolite, imperfect
il-	Not (before l)	illegal, illegible, illogical, illiterate, illicit
ir-	Not (before r)	irregular, irresponsible, irrelevant, irreversible, irrational
mis-	Wrongly; badly	misunderstand, misspell, mislead, misbehave, misplace
non-	Not	nonsense, non-fiction, non-stop, non-essential, non-verbal
anti-	Against	anticlockwise, antisocial, antibacterial, antifreeze, antidote

Helpful Hint: Notice how in- changes to im-, il-, or ir- depending on the first letter of the root word. This is to make the word easier to say. You would not say "inpossible" — it is much easier to say "impossible"!

Prefixes That Show Size, Number, or Amount

Prefix	Meaning	Example words
bi-	Two	bicycle, bilingual, binoculars, biweekly, bisect
tri-	Three	triangle, tricycle, trilogy, tripod, triple
multi-	Many	multiply, multicultural, multimedia, multitask, multilingual
semi-	Half; partly	semicircle, semifinal, semi-detached, semicolon, semi-precious
mono-/uni-	One	monologue, monopoly, uniform, unicorn, unique
micro-	Very small	microscope, microphone, microchip, microbe, microcosm
mega-	Very large	megaphone, megabyte, megalith, megacity, megastar
mini-	Small	miniature, minibus, minimum, miniskirt, minimize

Prefixes That Show Position or Direction