Clauses of Purpose Lesson: Definition, Uses, and Examples

Lesson Overview

• What Are Clauses of Purpose?
• Ways to Express Purpose in English
• Common Mistakes and Misconceptions

When we talk or write, we often need to explain why someone does something. For example, if you say, "I am studying," people might ask "Why are you studying?" Clauses of purpose help us answer that question by adding information about purpose or intention. In simple terms, a purpose clause tells us why an action is done. Learning to use these clauses will make your writing and speaking clearer and more meaningful.

What Are Clauses of Purpose?

A clause of purpose is a part of a sentence that explains the purpose or reason for an action. It answers the question "Why?". Consider this sentence:

• Main clause: I study hard (What do I do?)
  
  
• Purpose clause: to get good grades (Why do I do it?)

Combined: "I study hard to get good grades."

In the combined sentence, "to get good grades" is a clause of purpose – it tells us why the person studies hard. Clauses of purpose are important because they connect actions with intentions. They help you explain motivations, goals, and reasons in a single clear sentence.

Ways to Express Purpose in English

There isn't just one way to express purpose – English has several useful structures. The meaning in all cases is similar ("X is done in order to achieve Y"), but the wording changes slightly. The most common structures to show purpose are:

• "to" + _base form of verb_** (infinitive)** – e.g. "I exercise to stay healthy."
  
  
• "in order to" + verb – e.g. "I exercise in order to stay healthy."
  
  
• "so that" + clause – e.g. "I exercise so that I stay healthy."
  
  
• "for" + noun (or gerund) – e.g. "I went to the park for a run." (noun) / "This tool is used for cutting wood." (gerund)
  
  

Each of these can be correct in different situations. Let's explore each structure, see how they differ, and learn when to use them.


Take This Quiz-

Clauses of Purpose Quiz

1. Using "to" + Verb (Infinitive of Purpose)

The simplest and most common way to express purpose is to use "to" followed by a verb. This is called the infinitive of purpose. It directly links an action to its goal.

• Examples:
  • I opened the window to get some fresh air.
    
    
  • They studied for hours to prepare for the test.
    
    
  • We wear coats in winter to stay warm.
    
    

In each example, the part after "to" explains why the action is done. "To get some fresh air" explains why I opened the window. This structure is very common in everyday English because it's short and to the point.

Why use "to + verb"? It's quick and straightforward. In speaking and writing, it's often enough to use "to" for expressing purpose. For example, instead of saying "I went to the library because I wanted to study," you can say "I went to the library to study." Both sentences convey the reason, but the second is more concise.

2. Using "in order to" and "so as to" (More Formal Purpose)

Sometimes we add extra words like "in order to" or "so as to" before a verb to express purpose. These phrases have the same meaning as "to + verb" – they still answer "why?" – but they make the purpose sound more explicit or formal. They are often used in academic or formal writing, or when we want to emphasize the purpose.

• "in order to" + verb:
  
  
  • She left early in order to catch the first train. (Why did she leave early? To catch the first train.)
    
    
  • I turned off the TV in order to focus on my homework.
    
    
• "so as to" + verb:
  
  
  • He wore gloves so as to avoid leaving fingerprints.
    
    
  • We whispered so as to not wake the baby.
    
    

Notice that "in order to" and "so as to" are generally interchangeable with a simple "to". For example, "She left early to catch the first train" means the same as the sentence with "in order to" above. The difference is in tone: "in order to" and "so as to" sound a bit more formal or intentional. They can also add clarity in longer sentences where just "to" might get lost or be confusing.

Negative Purpose: When expressing a purpose not to do something (to avoid an outcome), English uses a slightly different form. Instead of saying "to not [do something]", we typically say "in order not to" or "so as not to".

• I put my phone on silent in order not to disturb the class. (Instead of "to not disturb the class.")
  
  
• He stayed quiet so as not to get noticed.
  
  

These sentences show an intended avoidance of something. A common mistake is to say "to not" in formal writing.

Why use these longer forms?

You might be wondering why anyone would use "in order to" when "to" alone says the same thing. It often comes down to style or clarity.

• Formality: In an essay or report, "in order to" might fit better.
  
  
• Emphasis: If you want to stress the purpose, the longer form can draw attention to it. For example, "The rules exist in order to protect students' safety" sounds a bit more emphatic than "The rules exist to protect students' safety." Both are correct; the choice depends on how formal or strong you want to sound.
  
  
  

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Clause vs Phrase: English Grammar Quiz

3. Using "so that" + Subject + Verb (Full Clause of Purpose)

Another common way to express purpose is with "so that", followed by a subject and a verb, forming a full subordinate clause. "So that" means "with the result or purpose that…" It's very useful when the purpose needs a separate subject or when we want to emphasize the outcome or ability that results from the action.

• I brought a map so that I wouldn't get lost.
  
  
• She studies hard so that she can get into a good high school.
  
  
• We left early so that we could beat the traffic.

In these examples, "so that" introduces a clause that explains the goal: I wouldn't get lost, she can get into a good high school, we could beat the traffic. Notice a few things here:

• The clause after "so that" has its own subject and verb (e.g., "she can get…"). This is different from the "to + verb" structure where there's no new subject mentioned.
  
  
• Often, the "so that" clause includes a modal verb like can, could, will, would, may, or might. For example, "so that she can get into a good high school," or "so that we could beat traffic." The modal verb fits the situation (present or future uses often get can/will, past or more hypothetical uses might get could/would).
  
  

Why choose "so that"?

One reason is when the person doing the action is different from the person benefiting or the one with the purpose. For instance:

• I will hide the gift so that you will be surprised.
  Here, I am doing the hiding, but you are the one who will be surprised (the purpose). Using "so that" makes it clear. If we tried to use "to" here, we'd run into a problem: "I will hide the gift to surprise you" actually works in this particular sentence (it implies I will surprise you), but consider another case:
  
  

Another reason to use "so that" is for clarity about outcomes. Sometimes using "to" could be interpreted in more than one way, especially in longer sentences. "So that" explicitly signals a purpose/result clause is coming, which can make complex sentences easier to follow.

4. Using "for" to Express Purpose

The word "for" can also indicate purpose, but it's used in specific ways:

• "for" + noun: This is very common. If you can state the purpose as a thing or event, you can often use "for."
  
  
  • I stopped by the store for milk. (I stopped by the store to get milk.)
  
  
• "for" + gerund (verb + ing): Sometimes purpose can be expressed with for followed by an -ing verb (which acts like a noun). However, this usage comes with a big warning: we usually don't use "for + -ing" to describe someone's intentional action in the moment.
  
  Instead, "for + -ing" often describes the general use of a thing or a general action, not a one-time intent.
  
  
  
  • A lawnmower is a machine for cutting grass. (Describes what it's used for generally.)This room is for studying. (Describes the intended use of the room.)I use a highlighter for marking important lines in the text. (Describes a habitual action or purpose of the object "highlighter.")
  
  
  
• "for" with a person + infinitive: There is a structure like "for someone to do something" which expresses purpose or necessity.
  
  For example, "I opened the door for my cat to come in." This means the same as "I opened the door so that my cat could come in." Here, "for my cat to come in" is a purpose phrase indicating why I opened the door. This structure is a bit more advanced and less common in basic sentences, but it's good to be aware of it.
  
  

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Understanding And Identifying Clauses Quiz

Common Mistakes and Misconceptions

Even when the rules seem straightforward, it's easy to slip up when you're actually writing or speaking. Let's address some common mistakes students make with purpose clauses, so you can avoid them:

• Mistake 1: Using "for" instead of "to" before a verb.
  
  Example: "I went to the computer lab for print my project."
  
  
  Correct it: Use "to" before the verb: "I went to the computer lab to print my project."
  
  Why "to print" shows purpose. Remember, for + verb (infinitive) is not the English structure; to + verb is.
  
  
• Mistake 2: Using "for + -ing" for a specific one-time action.
  
  Example: "She came here for discussing the issue."
  This sounds unnatural (or incomplete).
  
  
  Correct it: "She came here to discuss the issue."
  
  
  Why: Coming somewhere to do something is a specific action with intention – the proper form is "to + verb." "For discussing" would be interpreted as a general purpose ("for discussing issues," meaning maybe the place is a forum or something). If you're ever unsure, default to "to + verb" for actions.
  
  
• Mistake 3: "So that to…" – doubling up unnecessarily.
  
  Example: "I took notes so that to remember the lesson."
  Here the person mixed two structures: "so that" and "to." You only need one.
  
  
  Fix: Decide one structure and stick to it:
  
  
  • "I took notes to remember the lesson." (using "to")
    
    
  • OR "I took notes so that I could remember the lesson." (using "so that" with a subject and modal).
    
    
    Both are correct. Just don't say "so that to…" together.
    
    
• Mistake 4: Misplacing "not" in negative purpose.
  
  Example: "We whisper in the library to not disturb others."
  
  
  This isn't a terrible mistake-many native speakers even talk like this-but in formal writing it's better to avoid it.
  
  
  Better: "We whisper in the library so as not to disturb others." or "... in order not to disturb others."
  
  
  Why: As discussed, the conventional phrasing for negative intent is putting "not" before the "to." Another alternative is to use "so that" in a negative way: "We whisper so that we do not disturb others." That's perfectly fine too.
  
  
• Mistake 5: Confusing "so that" (purpose) with "so…that" (result).
  Look at these sentences:
  
  
  • "She practiced a lot so that she could win the contest." (purpose – she practiced with the intention of winning)
  
  
  It's easy to see "so that" and think it's the same as the "so [adjective/adverb] that" structure, but they are different. "So that" always means a purpose or intent (and usually has a subject right after it).
  
  "So + adjective + that" or "so + adverb + that" describes a result or outcome. For example, "It was so hot that we left early" describes a result of the heat, not anyone's purpose.
  
  If you keep a mental note that "so that" = in order that, and "so [adj] that" = as a result, you'll avoid mixing these up.
  
  

By being mindful of these common issues, you can write purpose clauses with confidence. It's absolutely normal to make some of these mistakes while learning. When you catch yourself making one, use it as a learning moment to reinforce the correct structure in your mind.