Infinitives of Purpose: Using “To” to Explain Why

Introduction

Have you ever wanted to explain why you do something — but you weren’t sure how to say it naturally? In English, one of the simplest and most common ways to express purpose is with the infinitive of purpose (to + verb). Mastering this structure will make your speaking and writing clearer, more natural, and more professional. In this post, you’ll learn exactly how to use “to” to explain why, with rules, examples, common mistakes, and practice exercises.

What Is an Infinitive of Purpose?

An infinitive of purpose is a structure that uses to + the base form of a verb to explain the reason or goal behind an action. It answers the question “Why?” For example:

• I went to the library to study.
• She called me to invite me to her party.
• They saved money to buy a new car.

In each sentence, the infinitive (to study, to invite, to buy) tells us the purpose of the main action. This structure is common in both formal and informal English, and it’s essential for B1–B2 learners who want to sound fluent.

Rules for Using Infinitives of Purpose

Follow these simple rules to use infinitives of purpose correctly:

1. Use “to” + base verb only. Never add “-ing” or change the verb form. Example: “I called to confirm” (not “to confirming”).
2. The infinitive must directly follow the main verb or object. Example: “He left early to catch the train.” (not “He left to early catch the train.”)
3. Do not use “for” before the infinitive. Use “to” alone. Example: “I am here to help” (not “for to help”).
4. You can use a negative infinitive: “not to” + verb. Example: “She stayed home not to miss the delivery.”
5. Use “in order to” or “so as to” for formal emphasis. Example: “He studied hard in order to pass the exam.” These are optional but useful in writing.

How to Use Infinitives of Purpose (Step by Step)

Here is a simple step-by-step guide to using this structure naturally:

1. Identify the main action. Start with a subject and a verb. Example: “I went to the store.”
2. Ask yourself: Why did I do that? The answer is your purpose. Example: “To buy milk.”
3. Combine them. Place the infinitive after the main clause. Example: “I went to the store to buy milk.”
4. Check the verb form. Make sure the infinitive is “to + base verb” (e.g., to buy, to see, to learn).
5. Practice with different subjects. Try it with “he,” “she,” “they,” and “we.” Example: “She called me to ask a question.”

Remember: The infinitive of purpose can also come at the beginning of a sentence for emphasis, though this is less common. Example: “To save money, we cook at home.”

Examples in Sentences

Here are 10+ sentences with the infinitive of purpose bolded for clarity:

• I wake up early to exercise every morning.
• He bought a new laptop to work from home.
• She is learning Spanish to travel in South America.
• They moved to the city to find better jobs.
• We are saving money to buy a house.
• He called his mother to wish her a happy birthday.
• I am reading this book to improve my vocabulary.
• She went to the gym to train for the marathon.
• They are building a new school to educate local children.
• He turned off his phone not to be disturbed during the meeting.
• We use a dictionary to check the meaning of new words.
• She took a taxi to arrive on time.

Common Mistakes with Infinitives of Purpose

Even advanced learners make these errors. Here are 4–5 common mistakes with corrections:

• Mistake 1: ❌ “I went to the store for to buy milk.”
  ✅ “I went to the store to buy milk.” (Never use “for” before the infinitive.)
• Mistake 2: ❌ “She called me for asking a question.”
  ✅ “She called me to ask a question.” (Use “to” + base verb, not “for” + -ing.)
• Mistake 3: ❌ “He left early for catch the train.”
  ✅ “He left early to catch the train.” (Use “to” + base verb, not “for” + base verb.)
• Mistake 4: ❌ “I am studying English for to get a better job.”
  ✅ “I am studying English to get a better job.” (Again, no “for” before “to.”)
• Mistake 5: ❌ “They went to the park for to have a picnic.”
  ✅ “They went to the park to have a picnic.” (Keep it simple: just “to” + verb.)

If you want to use “for,” you must follow it with a noun or noun phrase, not a verb. Example: “I went to the store for milk.” (Here “milk” is a noun, not a verb.)

Quick Summary

• Use to + base verb to explain why you do something.
• Never add “for” before the infinitive.
• Use not to for negative purposes.
• For formal writing, you can use in order to or so as to.
• The infinitive usually comes after the main clause, but can start a sentence for emphasis.

Practice Exercises

Fill in the blanks with the correct infinitive of purpose (to + verb). Answers are below.

1. I am going to the supermarket __________ (buy) some vegetables.
2. She joined a gym __________ (get) fit.
3. He turned down the music __________ (not disturb) his neighbors.
4. They are taking a taxi __________ (arrive) on time.
5. We are studying hard __________ (pass) the final exam.

Answers:

1. to buy
2. to get
3. not to disturb
4. to arrive
5. to pass

Conclusion

Using infinitives of purpose is one of the easiest ways to sound more natural when explaining why you do things. Just remember: to + base verb, no “for” before the infinitive, and practice with real-life examples. Start using this structure today — in your conversations, emails, and writing — and you’ll see immediate improvement in your English fluency.

FAQ

1. Can I use “for” instead of “to” for purpose?

Yes, but only with a noun or noun phrase, not a verb. For example: “I went to the store for milk.” If you want to use a verb, you must use the infinitive: “I went to the store to buy milk.” Never say “for to buy.”

2. What is the difference between “to” and “in order to”?

They have the same meaning, but “in order to” is more formal and emphatic. Example: “He studied hard to pass” (neutral) vs. “He studied hard in order to pass” (more formal). Both are correct; choose based on context.

3. Can I start a sentence with an infinitive of purpose?

Yes, you can! But it is less common in everyday speech. Example: “To save money, we cook at home.” This puts emphasis on the purpose. Be careful to add a comma after the infinitive phrase when it starts the sentence.

4. Is “to + verb” always an infinitive of purpose?

No. “To + verb” can also be part of other structures, such as after certain verbs (e.g., “I want to go“) or as a subject (e.g., “To travel is fun”). The infinitive of purpose specifically answers why an action is done. To identify it, ask: “Why did this happen?” If the answer is the infinitive, it is a purpose infinitive.