What is the infinitive of purpose?
The infinitive of purpose is a grammar structure used to explain the reason or intention behind an action. It answers the question 'why?' by using 'to + verb'. This structure is common in both spoken and written English and allows you to express your goals or the goals of others in a clear, concise way. For example, if someone asks why you're going to the library, you can respond with a purpose infinitive: 'I'm going to the library to study for my exam.'
How to form and use the infinitive of purpose
The structure is straightforward: use any verb in its infinitive form (to + base verb) at the end of a sentence or clause to show intention or reason. The infinitive of purpose always follows the main action verb. You do not need to use 'in order to' or 'so that'—the simple 'to' is usually sufficient. However, 'in order to' can be used for emphasis or in formal contexts. The negative form uses 'in order not to' or 'to avoid + gerund'.
When to use the infinitive of purpose
Use this structure when you want to state the goal or intention of an action. It's particularly useful in formal writing, explanations, and instructions. The infinitive of purpose works well in both simple and complex sentences. It's more common and natural than alternatives like 'so that' when the subject of both clauses is the same. If the subjects differ, you may need to use 'so that + clause' instead.
Infinitive of Purpose vs Other Purpose Structures
| Criterion | to + Infinitive | in order to | so that | to avoid + gerund |
|---|---|---|---|---|
| Form | to + base verb (e.g. to study) |
in order to + base verb (e.g. in order to study) |
so that + subject + modal/auxiliary + verb (e.g. so that she can study) |
to avoid + verb + -ing (e.g. to avoid making) |
| When to use | Everyday, neutral contexts; the most common way to express purpose when the subject of both clauses is the same | Formal or written contexts; when you want to be very explicit about purpose; same subject in both clauses | When the subject of the purpose clause is different from the main clause, or when a modal verb (can, could, will, would) is needed | When the purpose is to prevent something negative from happening; same subject in both clauses |
| Same / different subject | ✅ Same subject only | ✅ Same subject only | ✅ Same subject ✅ Different subject |
✅ Same subject only |
| Formality level | Neutral — suitable for both spoken and written English | Formal — more common in academic, professional, and written texts | Neutral to informal — common in both spoken and written English | Neutral — used in everyday speech and writing |
| Positive example | She went to the library to study for her exam. | She went to the library in order to study for her exam. | She left early so that her brother could use the car. | He read the instructions carefully to avoid making a mistake. |
| Negative example | She stayed home not to waste money on transport. (less common; so as not to is preferred in negatives) |
She stayed home in order not to waste money on transport. | He spoke quietly so that he wouldn't wake the baby. | She took an umbrella to avoid getting wet. (the gerund itself carries the negative sense) |
| Question example | Why did she go to the library? — To study for her exam. | What did she do in order to improve her grade? | Did she leave early so that you could use the car? | What did he do to avoid repeating the error? |
| Key signal words / clues | why, because, purpose, goal, aim — the simplest answer to "Why?" | in order, explicit purpose, formal writing, essay, report | different person, can/could/will/would, enable, allow, ensure | avoid, prevent, stop, not + verb-ing, negative outcome |
| Can follow a noun / pronoun? | Yes — I have a plan to save money. | No — it only follows a main clause | No — it introduces a full clause | No — it only follows a verb or clause |
| 🔑 Key Difference: Use to + infinitive (or the more emphatic in order to) for straightforward positive purpose when both the main and purpose clause share the same subject — to + infinitive is neutral while in order to is more formal. Switch to so that whenever the subjects differ or when a modal verb (can, could, will, would) is required, as neither to nor in order to can introduce a full clause with its own subject. Choose to avoid + gerund exclusively when the purpose is to prevent a negative result — the gerund after avoid already carries the negative meaning, so no extra "not" is needed. In short: same subject + positive goal → to / in order to; different subjects or modal needed → so that; preventing something bad → to avoid + -ing. | ||||
Formula
✔ Positive
Subject + main verb
+
to + infinitive
She works hard to achieve her goals.
✖ Negative
Subject + main verb
+
to avoid + gerund
+
or in order not to + infinitive
He left early to avoid the traffic.
Formula
Subject + main verb
+
in order to + infinitive
We saved money in order to buy a house.
Examples
I'm learning English to improve my career prospects.
Personal goal · Everyday usage
She travelled to Spain to visit her family.
Reason for action · Travel context
The government raised taxes to fund the healthcare system.
Formal explanation · Policy context
He took a course in order to qualify as an engineer.
Emphasis on purpose · Professional context
We left the party early to catch the last train.
Practical reason · Social situation
She exercises regularly to maintain her health.
Ongoing purpose · Health context
When to use it
Professional explanations
Explain the purpose of business actions or decisions clearly.
"We implemented new software to streamline our workflow."
Educational goals
State why you're doing something in an academic context.
"I'm reading this article to understand the topic better."
Written instructions
Use in formal writing, guidelines, or explanations.
"Add salt to enhance the flavour of the dish."
Answering 'why' questions
Respond naturally when someone asks about your intention.
"Why are you calling? To confirm our meeting tomorrow."
Signal words
to
in order to
so as to
in order not to
to avoid
Common Mistakes
✕
Wrong
I'm going to the shop for buying milk.
✓
Correct
I'm going to the shop to buy milk.
Use infinitive 'to buy', not 'for buying'. The gerund is incorrect here.
✕
Wrong
She studied hard to pass the exam and to get a good grade.
✓
Correct
She studied hard to pass the exam and get a good grade.
Avoid repeating 'to' in a list. Use it only once for parallel structures.
✕
Wrong
He took an umbrella to it not to rain.
✓
Correct
He took an umbrella to avoid the rain. / He took an umbrella in order not to get wet.
Use 'to avoid + gerund' or 'in order not to' for negative purpose, not 'to not'.
✕
Wrong
We came early for understanding the instructions.
✓
Correct
We came early to understand the instructions.
Use 'to + infinitive' for purpose, not 'for + gerund'.
KEY TAKEAWAYS
What to Remember
- Use 'to + infinitive' to express the reason or intention behind an action.
- The infinitive of purpose answers the question 'why?' in a sentence.
- Place the infinitive of purpose after the main verb to show intention.
- Don't use a gerund (verb + -ing) when expressing purpose; always use infinitive.
- The subject of the infinitive is usually the same as the main clause subject.