In English grammar, an infinitive is the base form of a verb preceded by "to" (e.g., to eat, to run, to be). Infinitives are versatile and can function as nouns, adjectives, or adverbs in a sentence. They are used to express purpose, intention, desire, and more.

Infinitive = to + base verb (e.g., to go, to see, to learn).
Can act as a subject, object, or complement.
Expresses purpose, intention, desire, or potential.

Use and Structure

How do you form a basic infinitive in English?

verb + -ing

base verb only

to + base verb

Use and Structure

The infinitive is formed by adding "to" before the base form of a verb: to + base verb (e.g., to eat, to sleep, to travel). Infinitives can also appear without "to" (called the bare infinitive) after certain verbs like can, will, must, let, make, and see.

Full infinitive: to + base verb (to study, to play)
Bare infinitive: base verb alone (see, make, let + verb)

Which are correct forms or uses of infinitives?

verb + -ed

bare infinitive after certain verbs

to + verb + -ing

to + base verb

Use and Structure

Functions of Infinitives

Infinitives serve multiple roles in a sentence:

1. As a Noun

Infinitives can act as the subject or object of a sentence.

Subject: To travel is my dream.
Object: She wants to learn Spanish.

2. To Express Purpose

Infinitives explain why something is done.

I study to pass the exam.
He called to ask a question.

3. After Certain Verbs

Some verbs are followed directly by an infinitive (not just any verb).

I hope to see you soon.
They plan to move next year.

How do you use an infinitive to express purpose?

past participle

-ing form

to + base verb

Functions of Infinitives

In which ways can infinitives be used?

To express purpose

Only in questions

As an adjective (to modify a noun)

As a noun (subject/object)

As an adjective for a noun (incorrect)

After certain verbs

Functions of Infinitives

Examples

Function	Example (Infinitive)	Translation/Meaning
As Subject	To read is relaxing.	Leer es relajante.
As Object	She likes to swim.	A ella le gusta nadar.
Purpose	I eat to live.	Como para vivir.
After Certain Verbs	They want to travel.	Quieren viajar.

Exercises

Identify the Infinitive: In each sentence, underline the infinitive and say its function.

He decided to leave early.
To forgive is divine.
She went to buy groceries.

Complete with Infinitives: Fill in the blanks with the correct infinitive form of the verb in parentheses.

I need _ (to finish) my homework.
They hope _ (to see) you soon.
We practice _ (to play) the piano.

Match Verbs to Infinitives: Which verbs from this list can be followed by an infinitive? (give a correct list)

want, enjoy, plan, finish, decide, avoid

Conclusion

Infinitives are a fundamental part of English verbs, expressing ideas about action in a flexible way.

Use "to + base verb" for classical infinitives.
Infinitives can function as nouns, express purpose, or follow special verbs.