When do I use for plus -ing instead of to?

Use for plus -ing to name the function of a thing: a cloth for polishing the lens, a hook for hanging the lantern. Do not use it for a person's aim after an action. Nia climbed for checking the lamp is the error; Nia climbed to check the lamp is the purpose pattern.

What is the difference between to and in order to?

Meaning: none. Nia stayed aloft to watch the channel and Nia stayed aloft in order to watch the channel aim at the same result. In order to and so as to are a little more formal and a little clearer in a long sentence. They are also the cleanest way to go negative: in order not to, so as not to.

How do I make a purpose negative?

Use so as not to or in order not to plus a verb: He left a note so as not to worry the next keeper. She wrapped the glass in order not to crack it. For not -ing is not a purpose form. To not and not to appear in speech; the so as / in order forms are safer in writing.

When do I use so that instead of to?

When the person (or thing) who benefits is not the person who acts, or when you need a modal in the purpose: She lit the lamp so that boats could see the headland. The infinitive of purpose wants one shared subject. A new subject needs a full clause after so that (or in order that).

English grammar · Intermediate

Infinitive of Purpose: To, In Order To, So As To, and For

Written by Eleanor Whitfield, Lead English Curriculum Editor · Reviewed September 2026

The infinitive of purpose uses to plus a verb to say why someone does something: Nia climbed the stairs to check the lamp. In order to and so as to do the same job with more formality, and they are the usual choice in the negative (so as not to wake the keepers). For plus -ing names the function of a thing (a cloth for polishing the lens), not a person's purpose, and that is the trap this page exists to catch.

Nia climbed the lighthouse stairs to check the lamp before the fog closed in.

to plus a verb naming the reason she climbed

What it is

English answers why with a to-infinitive attached to an action: she climbed to check the lamp, they lit the foghorn to warn the boats, he stayed aloft to watch the channel. The to-phrase is not the object of the first verb; it is an adverbial of purpose. In order to and so as to are longer versions of the same pattern, useful when you want a pause or a negative (in order not to, so as not to). For plus -ing is a different job. It names what an object is for (a cloth for polishing, a hook for hanging the lantern), not why a person did something. I climbed for checking the lamp is the error.

Nia climbed the stairs to check the lamp. (person's purpose: to-infinitive) This cloth is for polishing the lens. (object's function: for + -ing)

How to spot it

If you can replace the phrase with in order to and keep a person's aim, you have an infinitive of purpose. If the subject is a tool, a room, or a button, and the phrase names its use, you want for plus -ing instead.

She walked out to the gallery to watch the channel. (to plus verb: her purpose)
They lit the foghorn to warn the incoming boats. (purpose of lighting it)
He left a note so as not to worry the next keeper. (so as not to: negative purpose)
This hook is for hanging the spare lantern. (for plus -ing: the hook's function, not a person's aim)

The infinitive page covers every job the infinitive does. This page is purpose only: why an action happens, how to make that purpose negative, and when for plus -ing is the wrong tool.

Infinitive of Purpose Quick Reference

Ways to express purpose

Form	Typical use	Example
to + verb	default purpose after an action	She climbed the stairs to check the lamp.
in order to + verb	more formal, or clearer in a long sentence	She stayed aloft in order to watch the channel.
so as to + verb	formal written purpose	They banked the stove so as to keep the lamp-room warm.
so as not to / in order not to + verb	negative purpose	He left a note so as not to worry the next keeper.
for + -ing	function of a thing, not a person's aim	a cloth for polishing the lens
so that + clause	purpose when the two verbs have different subjects	She lit the lamp so that boats could see the headland.

Common Infinitive of Purpose Examples in English

Grouped by the purpose pattern, because to, in order to, so as to, and for plus -ing are not free variants:

To + Verb (Default Purpose)

Nia climbed the lighthouse stairs to check the lamp.: why she climbed: to plus a verb
They rowed out to inspect the landing stage.: purpose of rowing
He opened the log to record the visibility.: purpose of opening the log
She leaned over the gallery to watch the channel.: purpose of leaning

The first verb is the action; the to-infinitive is the reason. You can often ask why and answer with the infinitive.

In Order To and So As To

She stayed aloft in order to watch the channel.: in order to: a clearer, more formal to
They banked the stove so as to keep the lamp-room warm.: so as to: written, same meaning as to
He waited for slack water in order to land the stores.: in order to after a longer first clause
The keepers rotated watches so as to stay alert.: so as to naming the shared aim

In order to and so as to mean the same as to. Use them when to would be easy to miss, or when you need a negative (so as not to).

Negative Purpose

He left a note so as not to worry the next keeper.: so as not to: the usual negative
She wrapped the spare glass in order not to crack it.: in order not to: the same job
They dimmed the kitchen lamp so as not to spoil their night vision.: negative purpose of dimming
He moved quietly in order not to wake the off-duty keeper.: in order not to plus a verb

To not check and not to check are both heard, but so as not to and in order not to are the clean written forms. For not checking is not a purpose phrase.

For + -ing (Function, Not Purpose)

This cloth is for polishing the lens.: the cloth's function
a hook for hanging the spare lantern: for plus -ing after a noun
The gallery is for watching the channel, not for storage.: what the place is used for
These boots are for walking the wet rocks.: the boots' function

For plus -ing describes what a thing is used for. It does not replace to after a person's action: She climbed to check, not she climbed for checking.

How the Infinitive of Purpose Works

One default form, two formal twins, and a for-pattern that belongs to objects, not to people.

To Plus a Verb Answers Why

After an action, to plus a base verb names the aim of that action. The two verbs usually share a subject: Nia climbed (Nia) to check (Nia). The infinitive is an adverbial, so it can move (To check the lamp, Nia climbed the stairs) though end position is more natural. It is not the object of climbed; climbed already has its object, the stairs.

They lit the foghorn to warn the incoming boats.

to warn is the reason for lighting, not the object of lit

Action, then to plus the aim.

In Order To and So As To Are Formal To

In order to and so as to mean the same as to. They add weight and they make the purpose easier to see in a long sentence. They are also the standard way to go negative: so as not to, in order not to. In order that exists, but it needs a full clause (in order that the boats could see). For most sentences, to is enough.

She stayed aloft in order to watch the channel. He left a note so as not to worry the next keeper.

in order to as a clear to; so as not to for a negative aim

In order to and so as to = a heavier to.

For Plus -ing Names a Thing's Function

For plus an -ing form is right after a noun that names a tool, a place, or a product: a cloth for polishing, a hook for hanging, boots for walking. It is wrong after a person's action when you mean purpose: Nia climbed for checking the lamp. The test is the subject. If a person did something in order to achieve something, use to. If you are labelling what an object is used for, use for plus -ing.

This cloth is for polishing the lens. Nia took the cloth to polish the lens.

for plus -ing on the cloth; to plus verb on Nia's action

People take to. Things take for + -ing.

Different Subjects Need So That

The infinitive of purpose wants the same person (or thing) to do both verbs. When the aim belongs to someone else, English switches to so that plus a clause with its own subject and a modal: She lit the lamp so that boats could see the headland. In order that is a formal twin. You cannot write She lit the lamp to boats see.

She lit the lamp so that boats could see the headland.

so that plus a new subject and a modal

New subject in the purpose: so that, not to.

Common Mistakes with Infinitive of Purpose

Incorrect: Nia climbed the stairs for checking the lamp.

Correct: Nia climbed the stairs to check the lamp.

For plus -ing names the function of a thing, not a person's purpose. After a person's action, English uses to plus a verb. For checking would only work in a cloth for checking the lamp, labelling a tool.

Incorrect: She lit the lamp for boats to see the headland.

Correct: She lit the lamp so that boats could see the headland.

When the purpose has a different subject, the infinitive of purpose is the wrong tool. So that plus a clause with a modal (could, can, would) gives the new subject a verb of its own.

Incorrect: He left a note for not to worry the next keeper.

Correct: He left a note so as not to worry the next keeper.

For does not combine with not to in a purpose phrase. The standard negatives are so as not to and in order not to. For not worrying is also wrong here, because the subject is a person with an aim.

Incorrect: They rowed out for inspect the landing stage.

Correct: They rowed out to inspect the landing stage.

For cannot be followed by a bare verb. If you insist on for, the next word must be an -ing form, and even then the meaning shifts to function (a boat for inspecting the stage). Purpose after an action is to plus a verb.

So That, In Case, and Negative Purpose

Purpose has neighbours: a different-subject clause, a precaution, and the not-to forms.

So that plus a clause

Use so that when the person who benefits is not the person who acts, or when you need a modal (can, could, will, would) in the purpose clause.

She lit the lamp so that boats could see the headland.: boats is a new subject
He left the stove banked so that the lamp-room would stay warm.: so that plus would
They rang the foghorn so that anyone in the channel would hear it.: anyone is not they

So that the boats to see is impossible. After so that you need a full clause, not an infinitive.

In case is not purpose

In case names a precaution against something that might happen, not an aim you are trying to achieve.

She packed a spare wick in case the first one failed.: precaution, not an aim
He took the storm lantern in case the fog thickened.: in case plus a clause, no infinitive
They left a note in case the relief keeper arrived early.: preparing for a possible event

In case to fail and in case of the first one failed are both wrong. In case takes a clause. In case of takes a noun (in case of fog).

Negative purpose forms

Prefer so as not to and in order not to in writing. To not and not to both occur in speech; for not -ing is not a purpose pattern.

He moved quietly so as not to wake the off-duty keeper.: so as not to: written default
She wrapped the spare glass in order not to crack it.: in order not to
They dimmed the kitchen lamp not to spoil their night vision.: not to: possible, less formal

Avoid for not waking and to don't wake. The negative belongs on the infinitive (not to) or on so as / in order (so as not to).

Quick Check: Infinitive of Purpose

Choose to, in order to, so as not to, for, or so that.

1. Nia climbed the stairs ___ check the lamp.

Answer: to / in order to

person's purpose: to plus a verb

2. This cloth is ___ polishing the lens.

Answer: for

object's function: for plus -ing

3. He left a note ___ worry the next keeper. (negative purpose)

Answer: so as not to / in order not to

the standard negative infinitive of purpose

4. She lit the lamp ___ boats could see the headland.

Answer: so that

new subject in the purpose clause

5. She packed a spare wick ___ the first one failed. (precaution)

Answer: in case

in case is precaution, not purpose

Infinitive of Purpose FAQs

What is the infinitive of purpose?: It is to plus a verb used to say why someone does something: Nia climbed the stairs to check the lamp. The to-phrase is not the object of the first verb; it is an adverbial of purpose. In order to and so as to mean the same thing with more formality, and they are useful in the negative: so as not to wake the keeper.
When do I use for plus -ing instead of to?: Use for plus -ing to name the function of a thing: a cloth for polishing the lens, a hook for hanging the lantern. Do not use it for a person's aim after an action. Nia climbed for checking the lamp is the error; Nia climbed to check the lamp is the purpose pattern.
What is the difference between to and in order to?: Meaning: none. Nia stayed aloft to watch the channel and Nia stayed aloft in order to watch the channel aim at the same result. In order to and so as to are a little more formal and a little clearer in a long sentence. They are also the cleanest way to go negative: in order not to, so as not to.
How do I make a purpose negative?: Use so as not to or in order not to plus a verb: He left a note so as not to worry the next keeper. She wrapped the glass in order not to crack it. For not -ing is not a purpose form. To not and not to appear in speech; the so as / in order forms are safer in writing.
When do I use so that instead of to?: When the person (or thing) who benefits is not the person who acts, or when you need a modal in the purpose: She lit the lamp so that boats could see the headland. The infinitive of purpose wants one shared subject. A new subject needs a full clause after so that (or in order that).