Infinitives of Purpose: Using “To” to Explain Why

Introduction

Have you ever wanted to explain why you do something in English? Maybe you go to the library, or you turn on your phone. The most natural and common way to answer “why” is with an infinitive of purpose — simply using “to + verb.” This structure is easy to learn, but many learners make small mistakes that can change the meaning. In this post, you will understand exactly how to use infinitives of purpose, see clear examples, and avoid common errors. Let’s make your English more natural and precise.

What Is an Infinitive of Purpose?

An infinitive of purpose is a phrase that begins with the word “to” followed by the base form of a verb. It answers the question “Why?” It tells the reason or goal behind an action.

For example:

• I went to the store to buy milk. (Why did I go? To buy milk.)
• She studies hard to pass the exam. (Why does she study? To pass the exam.)

The structure is simple: Subject + verb + (object) + to + base verb + (rest of sentence). The infinitive always stays in the base form, no matter the tense of the main verb.

Rules for Using Infinitives of Purpose

1. Use “to” + base verb, not “for” + verb-ing. Many learners say “I went there for buying milk.” This is incorrect. Use “to buy.”
2. The infinitive must express the purpose of the main action. It cannot describe a result or a different action. Example: “He called to invite her” (purpose), not “He called to hear the news” (if the call was a result).
3. Do not use “to” with “ing” forms. “To swimming” is wrong. Always use the base verb: “to swim.”
4. You can use “in order to” or “so as to” for more formal or emphatic purpose. Example: “She left early in order to catch the bus.” This is optional but useful.
5. The infinitive of purpose can come at the beginning of a sentence for emphasis. Example: “To save money, I cook at home.” Note the comma after the infinitive phrase.

How to Use Infinitives of Purpose

Follow these steps to use them correctly in your own sentences.

Step 1: Identify the action and the reason.
Think of what you do and why you do it. For example: You open a book. Why? You want to learn.

Step 2: Write the main action in a sentence.
Example: “I open a book.”

Step 3: Add “to” + the reason verb.
Example: “I open a book to learn.”

Step 4: Check if the infinitive clearly answers “why.”
Ask yourself: Why do I open a book? To learn. Yes, it works.

Step 5: For negative purpose, use “to avoid” or “so as not to.”
Example: “I close the window to avoid the cold.” Or: “I whisper so as not to wake the baby.”

Step 6: Practice with different tenses.
Past: “She called to confirm the reservation.”
Future: “He will call to confirm the reservation.”
Present: “I call to confirm every time.”

Examples in Sentences

• I went to the gym to exercise.
• She saved money to buy a new laptop.
• They arrived early to get good seats.
• He turned on the light to see better.
• We use this app to track our expenses.
• I called you to ask a question.
• She is studying to become a doctor.
• He left work early to pick up his children.
• They built a fence to protect the garden.
• I am writing this post to help you learn.
• She closed the door to keep the noise out.
• We take notes to remember important points.

Common Mistakes

• Mistake 1: Using “for” + verb-ing instead of “to” + verb.
  ❌ I went to the store for buying milk.
  ✅ I went to the store to buy milk.
• Mistake 2: Using “to” + verb-ing (gerund) instead of base verb.
  ❌ She called to inviting me to the party.
  ✅ She called to invite me to the party.
• Mistake 3: Forgetting the comma when the infinitive starts the sentence.
  ❌ To save money I cook at home.
  ✅ To save money, I cook at home.
• Mistake 4: Using “to” for a result, not a purpose.
  ❌ He woke up late to miss the bus. (This sounds like he wanted to miss the bus.)
  ✅ He woke up late and missed the bus. (This explains the result, not purpose.)
• Mistake 5: Using “to” with a negative purpose incorrectly.
  ❌ I left early to not be late.
  ✅ I left early so as not to be late. Or: I left early to avoid being late.

Quick Summary

• Use “to” + base verb to explain why you do something.
• It answers the question “Why?”
• Never use “for” + verb-ing for purpose.
• For negative purpose, use “to avoid” or “so as not to.”
• You can start a sentence with the infinitive — add a comma after it.
• The infinitive form never changes, even with different tenses.

Practice Exercises

Fill in the blanks with the correct form of the verb in parentheses. Use an infinitive of purpose.

1. She opened the window ________ (let) in fresh air.
2. He bought a new phone ________ (take) better photos.
3. We are saving money ________ (travel) to Japan.
4. I called the office ________ (confirm) my appointment.
5. They left early ________ (avoid) traffic.

Answers:

1. to let
2. to take
3. to travel
4. to confirm
5. to avoid

Conclusion

Infinitives of purpose are one of the simplest and most useful tools in English. They help you explain your reasons clearly and naturally. By following the rules and practicing the examples, you will sound more fluent and confident. Remember: when you want to say why, just use “to” plus the base verb. Keep practicing, and soon it will feel automatic.

FAQ

1. Can I use “to” with a noun to show purpose?

No. “To” + noun usually shows direction (e.g., “I went to the store”). To show purpose, you must use “to” + base verb. If you want to use a noun, you can say “for” + noun (e.g., “I went for milk”). But for actions, always use “to” + verb.

2. What is the difference between “to + verb” and “for + verb-ing”?

“To + verb” is the standard way to express purpose. “For + verb-ing” is sometimes used to describe the function of a thing (e.g., “This tool is for cutting paper”), but it is not used for personal actions or goals. For personal reasons, always use “to + verb.”

3. Can I use an infinitive of purpose with “be” verbs?

Yes, but it is less common. For example: “The reason is to help you.” Here, “to help” explains the purpose of the reason. More often, you will use it with action verbs like “go,” “call,” “buy,” etc.

4. Is “in order to” always necessary?

No. “In order to” is more formal and emphatic, but in everyday English, simply using “to” is fine. For example, “I went to the store to buy milk” is natural. “I went to the store in order to buy milk” is correct but more formal. Use “in order to” when you want to sound very clear or formal.