Prefixes

A prefix is a group of letters added to the beginning of a word to change its meaning. By learning prefixes, you can work out the meanings of unfamiliar words and use them accurately in your writing.

What You'll Learn

• How to recognise and use all major prefix types covered in earlier levels: un-, re-, pre-, mis-, dis-, in-, im-, ir-, il-, over-, and under-
• How adding a prefix changes a word's meaning without changing its word class
• How to identify prefixed words and explain their effects in varied and more complex contexts
• How to avoid common spelling errors when attaching prefixes to base words

When to Use

1. To reverse or undo an action: "The teacher asked us to redo the experiment because the results were unreliable."
2. To show the opposite meaning: "It is impolite to interrupt someone who is speaking during a group discussion."
3. To indicate something done wrongly or badly: "She misunderstood the instructions and answered the wrong question on the comprehension paper."
4. To show excess or insufficiency: "The chef had overcooked the noodles, so they were soft and mushy. The soup was also undercooked."
5. To indicate something done before or in advance: "The committee held a preview of the art exhibition before it opened to the public."

How to Form

Adding a Prefix

A prefix is attached directly to the front of a base word. In most cases, you do not drop or add letters -- simply join the prefix to the base word.

Negative Prefixes and Their Spelling Patterns

The negative prefixes in-, im-, ir-, and il- all mean "not," but they change form depending on the first letter of the base word.

Prefix Meaning Groups

Key Rules

1. Do not change the spelling of the base word: When you add a prefix, keep the base word intact. Write mis + spell = misspell (two s's), not "mispell". Write un + necessary = unnecessary (two n's), not "unecessary".

2. A prefix changes meaning, not word class: Adding a prefix to an adjective gives you another adjective (happy → unhappy). Adding a prefix to a verb gives you another verb (do → undo). The word class stays the same.

3. Choose the correct negative prefix: Use im- before words starting with m or p, ir- before r, and il- before l. For most other words, use in- or un-. When in doubt, check which prefix sounds natural with the base word.

4. "un-" and "dis-" are not always interchangeable: Some words take only one prefix. You can say unkind but not "diskind". You can say disappear but not "unappear". Learn common pairs rather than guessing.

5. "over-" and "under-" are opposites: They often appear with the same base words to show excess and insufficiency. Overestimate means to guess too high; underestimate means to guess too low. Overcooked means cooked too long; undercooked means not cooked enough.

6. "re-" means again, not just any repetition: Use re- to show an action done a second time: reread (read again), rewrite (write again). Do not confuse it with words where "re" is part of the root, such as "receive" or "remember" -- these are not prefixed words.

Common Mistakes

Clue Words

Opposite / Negation clues (un-, dis-, in-, im-, ir-, il-)

not, opposite of, lacking, without, the reverse of

Repetition clues (re-)

again, once more, a second time, back to the original state

Advance / Prior clues (pre-)

before, in advance, earlier, ahead of time

Error clues (mis-)

wrongly, badly, incorrectly, by mistake

Excess clues (over-)

too much, excessively, more than needed

Insufficiency clues (under-)

too little, not enough, below the expected level

Tip: When you see a long or unfamiliar word in a reading passage, check whether it begins with a prefix you recognise. Peel off the prefix, find the base word, and then add the prefix meaning back. For example, irresponsible = ir (not) + responsible = not responsible. This strategy works for hundreds of English words.

Practice Tips

1. Peel-and-reveal method: Cover the prefix with your finger and read the base word first. Then uncover the prefix and combine the meanings. This helps you quickly decode unfamiliar prefixed words in comprehension passages.

2. Prefix-sorting exercise: Take a list of words and sort them by prefix type (negative, repetition, excess, etc.). This trains your brain to recognise prefix patterns automatically during examinations.

3. Check the spelling carefully: After writing a prefixed word, look at the join between the prefix and the base word. If both the prefix and the base word have the same letter at the boundary, you need both letters: mis + spell = misspell, un + natural = unnatural, il + legal = illegal.

4. Context confirmation: After identifying a prefixed word, re-read the sentence to confirm your understanding. Ask yourself: "Does the prefix meaning make sense here?" If overjoyed appears in a happy context, then over- here means "extremely" (not "too much"), which fits.

Quick Reference