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Word Study · Prefixes

Prefixes un-, re- and pre-: One Small Part Changes the Meaning

Learn what un-, re- and pre- mean, build new words from a base word, and spot the tricky words that only look like they have a prefix.

Grades 3–5 · 16 practice questions · Original material
Learning objectiveExplain the meaning of un- (not, or reverse), re- (again, or back) and pre- (before); use them to work out and spell new words; and check that the rest of the word is a real base word before deciding a word has a prefix.

The idea

A prefix is a word part added to the beginning of a base word. It changes the meaning, but the base word keeps its spelling. Lock becomes unlock. Read becomes reread. Heat becomes preheat.

un- usually means not (unhappy means not happy) or does the opposite of an action (unlock is the opposite of lock). re- usually means again (redo means do again) or back (repay means pay back). pre- means before (preview means view before).

Here is a quick test. Cover the prefix. Is what is left a real word whose meaning fits? In unfair, fair is a real word, and unfair means not fair, so un- is a prefix. In uncle, cle is not a word, so the un in uncle is not a prefix. In ready, ady is not a word, so re is just part of the spelling.

Adding a prefix never changes the spelling of the base word. That is why unnatural has two n's (un + natural) and reenter has two e's (re + enter). Some dictionaries write re-enter with a hyphen; both spellings are used in Canada.

Word bank

unlock

verb · un-LOK

to open a lock; the opposite of lock

Example: Dad unlocked the front door.

unfair

adjective · un-FAIR

not fair

Example: It felt unfair that only one team got a snack.

unkind

adjective · un-KYND

not kind; mean

Example: Laughing at someone's mistake is unkind.

unpack

verb · un-PAK

to take things out of a bag or box; the opposite of pack

Example: We unpacked our suitcases after the trip.

unsafe

adjective · un-SAYF

not safe; dangerous

Example: Thin ice is unsafe to walk on.

reread

verb · ree-REED

to read again

Example: I reread the question before answering.

rebuild

verb · ree-BILD

to build again

Example: They rebuilt the sandcastle after the wave.

refill

verb · ree-FIL

to fill again

Example: Please refill your water bottle.

repay

verb · ree-PAY

to pay back

Example: I will repay the two dollars tomorrow.

reappear

verb · ree-uh-PEER

to appear again

Example: The sun reappeared after the storm.

preheat

verb · pree-HEET

to heat before using

Example: Preheat the oven before baking the muffins.

preview

noun · PREE-vyoo

a look at something before it happens or comes out

Example: We watched a preview of the new movie.

preschool

noun · PREE-skool

a school for young children before kindergarten

Example: My little brother goes to preschool.

pretest

noun · PREE-test

a short test before you learn something, to see what you already know

Example: The spelling pretest showed which words I knew.

Worked examples

Example 1 · Work out a new word

What does unbreakable mean?

  1. Find the prefix: un-, meaning not.
  2. Look at the rest: breakable, meaning able to be broken.
  3. Put them together: not able to be broken.

Unbreakable means it cannot be broken.

Example 2 · Choose the prefix

Which prefix makes a word meaning 'to write again'? write → ___write

  1. 'Again' is the meaning of re-.
  2. Add it to the front without changing write.

rewrite

Example 3 · Is it really a prefix?

Does the word present have the prefix pre-?

  1. Cover pre. What is left is sent.
  2. Sent is a real word, but 'before sent' does not match the meaning of present (here, now, or a gift).
  3. The meaning test fails, so treat pre as part of the word, not a prefix you can use to work out the meaning.

No. In present, pre does not mean before.

Example 4 · Keep the base word's spelling

Add un- to necessary.

  1. un + necessary.
  2. Do not drop a letter: both the n from un and the n at the start of necessary stay.

unnecessary (two n's)

Common mistakes

Thinking every word that starts with un, re or pre has a prefix.

Why this fails: Uncle, ready, real and pretty only look that way. Cover the letters and check that a real base word with a matching meaning is left.

Dropping a letter when adding the prefix.

Why this fails: The base word does not change: un + natural = unnatural, re + enter = reenter.

Mixing up un- and re-.

Why this fails: Unpack is the opposite of pack; repack means pack again. They mean different things.

Making up words such as "ungood".

Why this fails: Not every base word takes un-. English often uses a different word instead (bad, not ungood). If you are unsure, check a dictionary.

Foundation

Foundation practice

Match each prefix to its meaning.

Meaning

1. What does re- mean in refill?

  1. not
  2. before
  3. again
  4. after
Meaning

2. What does pre- mean in preheat?

  1. before
  2. again
  3. not
  4. too much
Meaning

3. What does unsafe mean?

  1. safe again
  2. very safe
  3. safe before
  4. not safe
Meaning

4. What does unlock mean?

  1. lock again
  2. do the opposite of lock
  3. lock before
  4. lock very tightly
Build

5. Add a prefix to make a word meaning 'to tell again': ___tell

Practice

Practice practice

Use the right word in a sentence.

Fill in

6. "The first drawing got wet, so I had to ___ it."

  1. undraw
  2. predraw
  3. redraw
  4. draw
Fill in

7. "It is ___ to cross the street without looking."

  1. resafe
  2. unsafe
  3. presafe
  4. safe
Fill in

8. "Before the trip, we watched a ___ video about the museum."

  1. review
  2. unview
  3. preview
  4. reviewed
Fill in

9. "When we got home, we ___ the groceries."

  1. unpacked
  2. prepacked
  3. repacked
  4. packed
Build

10. Write the word that means 'not known'.

Build

11. Write the word that means 'to enter again'.

Think

Think practice

Check whether it is really a prefix.

Real prefix?

12. Which word does NOT contain the prefix un-?

  1. unhappy
  2. untie
  3. uncle
  4. unfair
Real prefix?

13. Which word does NOT contain the prefix re-?

  1. rebuild
  2. ready
  3. reread
  4. repay
Real prefix?

14. Does pretty contain the prefix pre-? Explain using the cover test.

Compare

15. What is the difference between unpack and repack?

Spelling

16. Which spelling is correct?

  1. unatural
  2. unnatural
  3. unnaturall
  4. un-natral

Answer key

  1. 1. again
    Refill means fill again.
  2. 2. before
    You preheat an oven before you bake.
  3. 3. not safe
    un- means not.
  4. 4. do the opposite of lock
    With actions, un- often reverses them: unlock, unpack, untie.
  5. 5. retell
    re- means again.
  6. 6. redraw
    You draw it again.
  7. 7. unsafe
    Crossing without looking is not safe.
  8. 8. preview
    A preview is a look before. A review is a look back afterward.
  9. 9. unpacked
    Taking things out of bags is the opposite of packing them.
  10. 10. unknown
    un + known. The n from un and the k-n of known both stay.
  11. 11. reenter (also written re-enter)
    re + enter keeps both e's. Both spellings appear in Canadian dictionaries.
  12. 12. uncle
    Cover un in uncle and cle is left, which is not a word. The others leave happy, tie and fair.
  13. 13. ready
    Cover re in ready and ady is left, which is not a word.
  14. 14. No. Cover pre and tty is left, which is not a word.
    The cover test shows pre is just part of the spelling.
  15. 15. Unpack means take things out (the opposite of pack). Repack means pack again.
    Different prefixes, different meanings, same base word.
  16. 16. unnatural
    un + natural. Keep both n's and the base word's spelling.

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