Infinitive After Adjectives Exercises

The pattern

Many English adjectives can be followed by a to-infinitive (to + the base form of a verb). The infinitive tells us what the adjective is about.

• I’m happy to help.
• She was surprised to see him.
• This puzzle is difficult to solve.

The structure is adjective + to + verb. Learners sometimes drop to or use an -ing form instead, so it helps to learn the main groups.

Main groups of adjectives that take a to-infinitive

Feelings and reactions. The infinitive says what caused the feeling: glad, happy, sad, pleased, surprised, shocked, relieved, delighted, disappointed, afraid, proud.

• We were relieved to hear the news.
• He was disappointed to lose.

Willingness and readiness. ready, willing, eager, keen, reluctant, prepared, able, likely, certain.

• She is ready to start.
• They are likely to arrive late.

Ease, difficulty and quality. easy, hard, difficult, impossible, safe, good, nice, interesting, useful.

• This app is easy to use.
• The box was too heavy to carry.

With this last group, the subject of the sentence is also the object of the infinitive. Do not add a pronoun after the verb: say The question is easy to answer, not easy to answer it.

It is + adjective + to-infinitive (for or of?)

The same adjectives often appear in a sentence that starts with it: It is easy to learn this app. You can add the person the statement is about with for:

• It is important for students to arrive on time.
• It is hard for me to wake up early.

For adjectives that describe a person’s character or behaviour, such as kind, nice, polite, rude, silly, clever, generous, use of:

• It was kind of you to help.
• It was rude of him to interrupt.

A quick test is to see whether the adjective can describe the person directly: You are kind works, so use of. Students are important does not describe the same idea, so use for.

Too and enough

• too + adjective + to-infinitive means a problem prevents something: The tea is too hot to drink.
• adjective + enough + to-infinitive means the quality is sufficient: He is old enough to drive.

Notice that enough comes after the adjective, and that a pronoun is not repeated: too hot to drink, not too hot to drink it.

Adjective + preposition + -ing

Some adjectives are followed by a preposition, and after a preposition the verb takes the -ing form, not the infinitive.

• She is good at swimming. (not at to swim)
• I’m interested in learning Italian.
• They are tired of waiting.

A few adjectives allow both: afraid of falling and afraid to fall are both possible, though the meaning can differ slightly. For more on choosing between the two forms, see the page on infinitive activities.

Exercise 1: Choose the correct form

1. I’m happy (to hear / hearing / hear) your news.
2. This puzzle is difficult (solve / to solve / solving).
3. She is ready (to start / starting / start).
4. It was kind (for / of) you to help.
5. The tea is too hot (to drink / to drink it).
6. He isn’t old enough (driving / to drive).
7. They were surprised (to find / finding) the door open.
8. She is good (at to swim / at swimming).
9. It is important (to / for) students to arrive on time.

Exercise 2: Correct the mistake

1. The question is easy to answer it.
2. I’m afraid to going alone.
3. It’s necessary of you to bring ID.
4. We were glad see them.

Exercise 3: Rewrite with the adjective as the subject

Rewrite each sentence so that the thing becomes the subject.

1. It is easy to use this app.
2. It is hard to open this jar.
3. It is impossible to forget that song.

Answers

Exercise 1

1. to hear
2. to solve
3. to start
4. of (kind describes the person)
5. to drink
6. to drive
7. to find
8. at swimming (preposition + -ing)
9. for (important does not describe the students’ character)

Exercise 2

1. The question is easy to answer.
2. I’m afraid to go alone. (or afraid of going alone)
3. It’s necessary for you to bring ID.
4. We were glad to see them.

Exercise 3

1. This app is easy to use.
2. This jar is hard to open.
3. That song is impossible to forget.

After you finish, try combining these structures in your own sentences. Mixed error-spotting practice is available in the sentence correction exercises, and the infinitive activities page covers verbs that are followed by an infinitive or a gerund.