Adjective + Infinitive: Easy to Read, Happy to Help
An adjective followed by a to-infinitive is one of the most common patterns in English: happy to help, easy to use, ready to go, too tired to think. The adjective describes a person or thing, and the infinitive says what the feeling, quality or difficulty is about.
The pattern looks like one structure, but it hides four different ones. In “She is happy to help”, she does the helping. In “This book is easy to read”, the book does not read anything; someone reads the book. Knowing which type you are using explains most of the mistakes learners make with it. (If you need a refresher on adjectives themselves, start with what is an adjective.)
Type 1: feelings and attitudes (happy to help)
After adjectives of feeling, the subject of the sentence is also the person who does the action in the infinitive.
- I’m happy to help. (I help.)
- We were sorry to hear the news.
- She was surprised to see him there.
- They’re afraid to ask questions in class.
- He was proud to represent his school.
Common adjectives in this group: happy, glad, pleased, delighted, sorry, sad, surprised, shocked, amazed, relieved, disappointed, proud, afraid, anxious, eager, keen, reluctant.
Afraid to and afraid of are both correct, with a small difference. “I was afraid to jump” means I did not dare to jump. “I was afraid of falling” means I feared that falling might happen. The second pattern, adjective + preposition + -ing, is covered in adjectives with prepositions.
Type 2: certainty and willingness (sure to win, ready to go)
These adjectives say how likely something is, or how prepared or willing someone is. Again, the subject does the action.
- They’re sure to win. / They’re certain to win. (I am sure they will win.)
- The price is likely to rise. Prices are unlikely to fall this year.
- Are you ready to order?
- He’s always willing to listen.
- You’re free to leave at any time.
- She was the first to arrive and the last to leave.
Note the difference between “She is sure to win” (the speaker is sure) and “She is sure that she will win” (she is sure). This is one place where the infinitive changes whose opinion it is.
Type 3: easy to read: the subject receives the action
This is the type that causes problems. After adjectives such as easy, hard, difficult, impossible, simple, nice, pleasant, safe, dangerous, interesting, comfortable, the subject of the sentence is the object of the infinitive.
- This book is easy to read. (= It is easy to read this book.)
- The instructions were hard to follow.
- Our new neighbour is nice to talk to.
- This chair is comfortable to sit on.
- Tap water here is safe to drink.
Three rules follow from this:
- Do not repeat the object. Say “This book is easy to read”, not “This book is easy to read it.” The book has already been named.
- Keep the preposition at the end. “nice to talk to”, “comfortable to sit on”, “easy to get along with”. Dropping it (“nice to talk”) is a common learner error.
- Do not use a passive infinitive. “The house is difficult to heat”, not “difficult to be heated”.
The same meaning can be expressed with it as a dummy subject: “It is easy to read this book.” Both are correct; the version that starts with the thing (“This book is easy to read”) is usually more natural when the thing is your topic.
Type 4: judging someone’s action (kind of you to come)
To say what you think of something a person did, use It is + adjective + of + person + to-infinitive:
- It was kind of you to come.
- It’s very generous of them to offer.
- It was silly of me to forget my keys.
- That was brave of her to speak up.
Adjectives used this way describe character: kind, nice, good, generous, thoughtful, polite, rude, brave, clever, careless, silly, stupid, selfish, wise. Compare of and for:
- It was nice of you to call. (calling was a nice thing you did; it describes you)
- It is important for you to call. (your calling is important; it does not describe you)
Use for + person after adjectives like important, necessary, easy, hard, possible, unusual: “It’s hard for me to wake up early.”
Too + adjective + infinitive, adjective + enough + infinitive
These two patterns say whether a quality stops something or allows it.
- The box is too heavy to lift. (So I can’t lift it.)
- She’s old enough to drive. (So she can drive.)
- The coffee was too hot to drink.
- Is the water warm enough to swim in?
Two points to watch: enough goes after the adjective (“tall enough”, not “enough tall”), and as with type 3, the object is not repeated (“too heavy to lift”, not “too heavy to lift it”). To say who is affected, add for + person: “The text was too small for me to read.”
Infinitive or -ing?
Some adjectives can be followed by either a to-infinitive or a preposition + -ing, sometimes with a change in meaning:
| To-infinitive | Preposition + -ing | Difference |
|---|---|---|
| I’m sorry to hear that. | I’m sorry for shouting. | Sorry + to: about news now; sorry for: apologising for a past action |
| She was afraid to say no. | She was afraid of saying the wrong thing. | Afraid to: didn’t dare; afraid of: feared a result |
| He’s interested to know the result. | He’s interested in learning Spanish. | Interested to: curious about one fact; interested in: general interest (more common) |
| I was glad to help. | (no -ing version) | Glad takes only the infinitive or a that-clause |
Some feeling adjectives can also be followed by a that-clause: “I’m glad (that) you came”, “We were surprised that the shop was closed.” Use the infinitive when the subject of both parts is the same person; use that when it changes.
Common mistakes
| Wrong | Right | Why |
|---|---|---|
| This question is difficult to answer it. | This question is difficult to answer. | The subject is already the object |
| She is nice to talk. | She is nice to talk to. | Keep the preposition |
| He isn’t enough old to vote. | He isn’t old enough to vote. | Enough follows the adjective |
| It was kind for you to help. | It was kind of you to help. | Character adjectives take of |
| I’m happy for helping you. | I’m happy to help you. | Happy + to-infinitive |
| The room is easy to be cleaned. | The room is easy to clean. | No passive infinitive after easy |
Practice
A. Correct the sentence if necessary.
- This software is simple to use it.
- It was very thoughtful of him to bring flowers.
- The bag was too heavy for carry.
- Our teacher is easy to talk.
- We were delighted to meet you.
- Is he enough tall to ride the roller coaster?
Answers: 1 simple to use. 2 correct. 3 too heavy to carry. 4 easy to talk to. 5 correct. 6 tall enough to ride.
B. Of or for?
- It was rude ___ them to leave without saying goodbye.
- It’s important ___ children to sleep well.
- It was clever ___ you to bring an umbrella.
- It’s hard ___ me to understand his accent.
Answers: 1 of; 2 for; 3 of; 4 for.
Quick answers
Can an adjective be followed by an infinitive? Yes: happy to help, easy to read, ready to go, likely to rain, kind of you to come.
What is an example of adjective + infinitive? “This recipe is easy to follow.” “I’m glad to see you.”
Why is it “easy to read”, not “easy to read it”? Because the subject (the book) is already the thing being read; repeating it with it doubles the object.
Is “enough” before or after the adjective? After: “warm enough”, “good enough to win”.
Related: predicate adjectives, where most of these patterns start, and postpositive adjectives, for adjective + complement after a noun (“a problem difficult to solve”).
Checked against Merriam-Webster, the Chicago Manual of Style and the AP Stylebook. Spotted an error? Tell us — see our editorial policy.
