Clauses of Purpose: Rules, Uses & Examples

A clause of purpose is a dependent clause that explains what someone intends to achieve by doing something. Finite purpose clauses commonly begin with so that or in order that.

The caretaker left the side gate unlocked so that the cyclists could enter the park before sunrise.

The main clause tells us what the caretaker did. The purpose clause explains why the gate was left unlocked and what the caretaker wanted to make possible.

Clauses of purpose express an intended outcome, which is not necessarily the same as what eventually happens.

So That and In Order That

So that and in order that introduce finite purpose clauses. Both connect an action with its intended outcome, but they differ in how commonly they are used.

So That

So that is the more natural choice in most everyday situations.

Aisha moved the reading lamp closer so that her grandfather could see the newspaper clearly.

Aisha moved the lamp, while her grandfather was the person expected to benefit from better lighting.

So that also works when the same person performs both actions:

Oliver marked the important pages so that he could find them quickly during the interview.

In informal English, that is sometimes omitted:

The guide slowed down so everyone could follow the directions.

This is a natural alternative to so that everyone could follow the directions.

In Order That

In order that expresses a similar purpose but is considerably more formal.

The court appointed an interpreter in order that the witness could give evidence clearly.

In ordinary conversation, so that would usually sound more natural:

The court appointed an interpreter so that the witness could give evidence clearly.

In order that is more likely to appear in formal documents, official communication, or deliberately formal writing.

Modal Verbs in Purpose Clauses

Purpose clauses often contain modal verbs such as can, could, will, would, may, and might.

The modal helps show what an action is intended to make possible or bring about. Both the time reference and the intended meaning influence the choice.

Can and Could

Can commonly expresses the ability or opportunity that an action is intended to provide.

Mira keeps a spare house key with her sister so that someone can get inside if she accidentally locks herself out.

The arrangement is intended to make access possible when needed.

When describing a past action, could is common:

The neighbours installed a handrail beside the steps so that their elderly father could use the entrance more safely.

The handrail was intended to make using the steps safer for him.

Will and Would

Will can express an expected future outcome.

Lena is saving copies of the family recipes so that her daughter will have them when she grows older.

Would often appears when the intended outcome is described from a past perspective.

The technician left a labelled diagram so that the night team would know how the cables were connected.

Compare:

Daniel shared the password so that his colleague could access the files.

Daniel shared the password so that his colleague would have access to the files.

The first emphasizes making access possible. The second presents having access as the intended outcome.

Both refer to a past action, so the distinction is not simply one of tense.

May and Might

May and might also appear in purpose clauses, particularly in formal writing.

The council published the proposal early so that residents might comment before the vote.

The purpose was to give residents an opportunity to comment.

In everyday English, could would usually sound more natural in this example.

Does a Purpose Clause Always Need a Modal?

No. A purpose clause can also contain the present simple.

I’ll leave the instructions on the table so that everyone knows where to find them.

Compare:

I’ll leave the instructions on the table so that everyone can find them.

The first focuses on everyone knowing the location. The second emphasizes making the instructions accessible.

Both express purpose without requiring the same verb form.

To, In Order To, and So As To

Purpose can also be expressed through an infinitive construction.

The most common forms are to, in order to, and so as to, followed by the base form of a verb.

Compare:

Elena visited the archive to examine the original photographs.

Elena visited the archive in order to examine the original photographs.

Elena visited the archive so as to examine the original photographs.

All three explain Elena’s reason for visiting the archive.

The simple to construction is generally the most natural and concise. In order to and so as to are somewhat more formal and can make the intended purpose more explicit.

Finite Purpose Clauses and Infinitive Constructions

There is an important grammatical distinction between these constructions.

A finite clause contains a finite verb form, such as could attend or would appear.

An infinitive construction uses a non-finite verb form, such as to capture or to give.

Traditional school grammar often calls these infinitive constructions infinitive phrases. In modern grammatical analysis, they can be described as non-finite clauses because they contain a verb without a finite verb form.

To + Infinitive vs. For + Noun or -ing

An infinitive can explain someone’s purpose in performing an action.

Nora went to the workshop to repair her bicycle.

This suggests that Nora intended to carry out the repair herself.

Compare:

Nora took her bicycle to the workshop for repairs.

This explains why she took it there without identifying who would repair it.

For + -ing is also common when describing the function or use of something.

The workshop has a separate workbench for repairing bicycles.

The workbench is intended for that activity.

Compare:

Incorrect: Nora went to the workshop for repairing her bicycle.

Correct: Nora went to the workshop to repair her bicycle.

The incorrect version is not a natural way to express Nora’s personal intention in ordinary English.

However, for + -ing has other grammatical uses. It can also introduce a reason:

Priya was thanked for helping the new students.

Here, the construction explains why Priya received thanks. It does not describe the purpose of an object.

Not Every To-Infinitive Expresses Purpose

The presence of to + verb does not automatically mean a sentence contains an infinitive of purpose.

Compare:

Sophie went upstairs to collect her notebook.

The infinitive explains why Sophie went upstairs.

Sophie wants to collect her notebook.

Here, to collect her notebook completes the meaning of wants. It does not explain the purpose of another action.

When the Person Performing the Intended Action Changes

Changing a purpose construction can change who is understood to perform the intended action.

Suppose a teacher moves a chair because a student needs a clearer view of a demonstration.

The first, third, and fourth sentences express the intended benefit for the student.

The second changes the natural interpretation because the teacher is understood to be the person who wants to see.

In everyday English, so that the student could see would generally sound more natural than in order for the student to see, although both constructions are grammatical.

Understanding the Subject of an Infinitive

In a simple purpose infinitive, the subject is usually unexpressed and understood from the main clause.

Ethan moved closer to the window to read the notice.

Ethan is understood to be the person reading the notice.

Some infinitive constructions allow a different subject to be stated explicitly.

The staff cleared the entrance in order for wheelchair users to enter safely.

Here, wheelchair users is the explicitly stated subject of to enter safely.

Compare:

The staff cleared the entrance so that wheelchair users could enter safely.

Both identify who was intended to enter. The second is usually the more natural choice in everyday communication.

Expressing Negative Purpose

Sometimes an action is taken to prevent something undesirable.

Common negative-purpose constructions include in order not to, so as not to, and so that followed by an appropriate negative verb form.

In Order Not To and So As Not To

These constructions are useful when the person taking the main action wants to avoid a particular outcome.

Clara handled the old photograph by its edges in order not to leave fingerprints on the surface.

James kept his phone on silent so as not to interrupt the presentation.

The standard word order is:

Correct: in order not to damage the painting

Correct: so as not to damage the painting

Not normally appears before to in these constructions.

So That With a Negative Clause

A finite purpose clause can identify a different person or thing involved in the unwanted outcome.

The ranger moved the warning signs closer to the footpath so that visitors wouldn’t disturb the nesting birds.

The ranger’s aim was to prevent the visitors from disturbing the birds.

Another example:

A family closed the kitchen door so that the sound of the blender wouldn’t wake the baby.

The negative clause identifies the disturbance the family wanted to prevent.

What About Lest?

Lest is a formal or literary conjunction used to introduce something someone wants to avoid.

The curator covered the fragile sculpture lest dust should settle on its surface.

A more natural contemporary version would be:

The curator covered the fragile sculpture so that dust wouldn’t settle on its surface.

Lest is useful to recognize in older or formal writing, but it is uncommon in everyday conversation.

Purpose, Reason, Result, and Precaution

Purpose explains what someone intends to achieve. Reason explains why an action happens. Result describes what follows from an event or situation.

Precaution is related but slightly different: someone takes action in preparation for something that might happen.

Consider:

A purpose describes an intended outcome, while a result describes a consequence presented as having occurred.

The separate lesson on clauses of reason explains how reasons can describe causes, motivations, and evidence supporting conclusions.

So That vs. So … That

These patterns can look similar, but they often express different relationships.

The organisers enlarged the signs so that visitors could find the correct entrance.

This expresses purpose. The organisers intended to make the entrance easier to find.

Compare:

The signs were so large that people could read them from across the courtyard.

This expresses a result associated with the signs’ size.

Result constructions with so … that commonly involve an adjective or adverb:

The instructions were so clear that nobody needed a second explanation.

They can also involve quantity expressions:

So many people arrived that the organisers opened a second entrance.

One further distinction matters: so that can sometimes introduce a result rather than a purpose.

The storm damaged the only bridge, so that the village was temporarily cut off.

This describes a consequence of the storm damage. It does not express anyone’s intention.

This result use of so that is more formal than the straightforward alternative:

The storm damaged the only bridge, and as a result, the village was temporarily cut off.

The meaning depends on the relationship being expressed, not just the presence of so that.

So That vs. In Case

So that usually introduces an outcome someone intends to bring about.

In case commonly introduces a possible situation for which someone prepares.

Compare:

Hannah saved a photograph of the receipt so that the accountant could check the amount.

The accountant’s ability to verify the amount is the intended benefit.

Hannah saved a photograph of the receipt in case the shop asked for proof of purchase.

The photograph was saved as a precaution against a possible request.

In Case vs. If

In case and if are not automatically interchangeable.

Compare:

I saved the venue’s address offline in case my internet connection failed.

The address was saved beforehand, as a precaution.

If my internet connection fails, I’ll use the saved address.

This describes what the speaker intends to do if the stated condition occurs.

The first sentence describes preparation for a possible problem. The second describes an action that depends on the condition being met.

Position and Punctuation of Purpose Clauses

Purpose clauses usually follow the action whose purpose they explain.

The teacher distributed the instructions early so that everyone could review them before the workshop.

A comma is normally unnecessary when the following purpose clause is closely connected to the main clause.

A finite purpose clause can also come first, although this arrangement is less common.

So that every participant could see the demonstration, the instructor moved the table closer to the centre of the room.

An introductory purpose clause is normally followed by a comma.

Infinitive purpose constructions can also appear in different positions.

The gardener placed a marker beside each plant to identify the new varieties.

To identify the new varieties, the gardener placed a marker beside each plant.

Both are grammatical.

When an introductory infinitive is used, the sentence should make its understood subject clear.

To avoid damaging the wall, Leo moved the cabinet a few inches at a time.

Leo is the person trying to avoid damaging the wall.

Clauses of Purpose: Practice With Answers

1. Identify the Purpose Clause

The community centre installed an adjustable reception desk so that visitors using wheelchairs could speak comfortably with the staff.

Which part of the sentence is the finite purpose clause, and what does it explain?

Answer:

So that visitors using wheelchairs could speak comfortably with the staff is the purpose clause.

It explains what the community centre intended to achieve by installing the desk.

2. Choose the Most Suitable Modal Verb

A group installed a temporary handrail last weekend because it wanted older residents to use the steps more safely during the event.

Complete the sentence:

The group installed a temporary handrail so that older residents ______ use the steps more safely.

A. can

B. could

C. will

Best answer: B.

The group installed a temporary handrail so that older residents could use the steps more safely.

Could naturally expresses an intended ability associated with a past action.

Other verb forms may be possible with a different time reference, but could best matches this situation.

3. Rewrite Without Changing Who Performs the Action

A mother lowered the kitchen blind because her son needed to read the instructions on a screen without glare.

Rewrite this sentence without changing its meaning:

The mother lowered the kitchen blind to read the instructions without glare.

Possible answer:

The mother lowered the kitchen blind so that her son could read the instructions without glare.

The original wording naturally suggests that the mother intended to read the instructions.

The revision makes clear that her son was expected to read them.

Another suitable version is:

The mother lowered the kitchen blind to give her son a clearer view of the instructions.

4. Express a Negative Purpose

Marcus turned off notification sounds because he did not want to interrupt his sister’s online interview.

Rewrite the sentence using so as not to.

Possible answer:

Marcus turned off notification sounds so as not to interrupt his sister’s online interview.

The infinitive construction expresses what Marcus wanted to avoid.

5. Purpose or Result?

Compare:

A. The organisers raised the platform so that people at the back could see the performance.

B. The platform was so high that everyone could see the performers.

Which sentence expresses an intended purpose, and which describes a result?

Answer:

A expresses purpose. The organisers raised the platform with the intention of improving visibility.

B expresses result. The sentence describes visibility as a consequence of the platform’s height.

Sentence A does not establish that the intended improvement was achieved.

6. In Case or If?

A traveller has downloaded an offline map because she is concerned that mobile reception may fail during a long drive.

Choose the expression that best completes each sentence.

A. She downloaded the map ______ mobile reception failed.

Answer: In case.

She downloaded the map in case mobile reception failed.

The download happened in advance as a precaution.

B. ______ mobile reception fails, she will use the downloaded map.

Answer: If.

If mobile reception fails, she will use the downloaded map.

The sentence describes what she intends to do if the condition occurs.

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