Printable worksheet helping students practice forming antonyms by adding the prefix 'un-' to common vocabulary words.

Let's solve this grammar worksheet step by step. The task is to complete each sentence using the prefix "un-" with one of the words from the box provided.

Words in the box:

- complicated
- healthy
- clear
- believable
- answered
- acceptable
- kind
- finished
- employed
- used
- afraid
- furnished
- able
- comfortable
- expected
- happy

We need to add the prefix "un-" to make a new word that fits logically in the sentence.

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1. Smoking isn't good for your body. It's very unhealthy.

✔ Correct! "Unhealthy" means not healthy.

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2. The company’s annual report is ________ I have to finish it by tomorrow’s.

→ We need a word that describes something not finished.
Use: unfinished

✔ unfinished

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3. I was ________ to go to the meeting yesterday because I was sick. I couldn’t go.

→ Can't go → not able → unable

✔ unable

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4. Of course, my teammates were ________ after we lost the game.

→ After losing, they were not happy → unhappy

✔ unhappy

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5. We like our math teacher. He makes difficult problems seem easy and ________.

→ Easy and understandable → not complicated → uncomplicated

✔ uncomplicated

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6. The new apartment we moved into doesn’t have any furniture. It’s ________.

→ No furniture → unfurnished

✔ unfurnished

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7. My brother doesn’t have a job. He’s still ________.

→ Not employed → unemployed

✔ unemployed

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8. It snowed yesterday – and it’s August! It’s ________!

→ Something unexpected → unexpected

✔ unexpected

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9. I don’t understand how to use this machine. The instructions are ________.

→ Hard to understand → unclear

✔ unclear

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10. Ouch! My new shoes are a little too small. They feel ________.

→ Not comfortable → uncomfortable

✔ uncomfortable

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11. Sue forgot to answer all the test questions. There were two questions ________.

→ Questions that weren’t answered → unanswered

✔ unanswered

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12. The car I bought is new. It’s completely ________.

→ New, so not used → unused

✔ unused

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13. Don’t like Sam. He’s not very nice. Sometimes, he can be ________.

→ Not kind → unkind

✔ unkind

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14. Mikey is only three years old but he is ________ of the dark.

→ Not afraid → unafraid

✔ unafraid

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15. You’re always late for work! It’s ________! You must come on time!

→ Not acceptable behavior → unacceptable

✔ unacceptable

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16. I was quite surprised when my boss gave us a holiday. It was ________!

→ Surprising → not expected → unexpected

✔ unexpected

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✔ Final Answers:

1. unhealthy
2. unfinished
3. unable
4. unhappy
5. uncomplicated
6. unfurnished
7. unemployed
8. unexpected
9. unclear
10. uncomfortable
11. unanswered
12. unused
13. unkind
14. unafraid
15. unacceptable
16. unexpected

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Explanation:

The prefix "un-" is commonly used to create antonyms (opposites) of adjectives and adverbs. For example:
- healthy → unhealthy
- able → unable
- happy → unhappy

We matched each sentence with the logical opposite meaning using the appropriate word from the box, then added "un-" to form the correct word.

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