英语日常语法:表达目的的常用方式

From VOA Learning 1 English, this is Everyday Grammar.

You may remember our earlier reports on infinitives 3 and gerunds. The infinitive 2 form of a verb can be either its most basic form or appear with the word to. A gerund is a verb that ends in –ing and acts as a noun 4.

Today, we learn that these forms can help us express the purpose for an action.

to + infinitive

Let's start with infinitives of purpose. Imagine you want to answer the question, "Why do you do that?"

For example, let's say you hear some friends talking:

Why do you listen to that podcast?

I do it to improve my listening skills.

When we express purpose with an infinitive, we are telling someone why we do an action.

But, often, when we answer a question, we don't answer in a complete sentence. Let's listen to this example.

Why do you listen to that podcast?

To improve my listening skills

This exchange shows that the verb phrase of purpose does not always appear with a subject.

in order to + infinitive

A more formal way to express purpose is by using in order to plus the infinitive form of the verb. Listen to this example:

I listen to the podcast in order to improve my listening skills.

You have probably never used the phrase in order to. We generally avoid it in spoken English; it sounds too formal. There are exceptions 5, such as in public speaking in academic, political or professional settings 6.

for + verb + ing

By now you may be wondering, "But what about the word 'for'? Doesn't that word also express purpose?"

The answer is yes.

Sometimes, the word for describes the purpose of a thing or answers the question "What is this thing (used) for?" In this case, for is followed by a gerund, or the –ing form of a verb. Remember that a gerund acts as a noun.

For example, you might be giving advice on how to keep a garden. Or, you might be demonstrating 7 the use of a gardening tool. Listen:

This tool is for weeding.

Here, the word for is followed by the gerund weeding.

Or, maybe you are responding to a question about what the tool is used for. Listen:

What is this tool (used) for?

It's for weeding.

When the subject of the sentence is a person or people, you can use the infinitive or for plus the gerund. Listen to these examples:

I use this tool for weeding.

I use this tool to weed the garden.

In these sentences, the subject is "I," or a person.

When the subject is a person, and we choose the infinitive to describe what we use something for, we generally include the object of the verb phrase. In this sentence, the verb phrase is to weed the garden. The object of the verb phrase is the garden.

for + object

We can also use for to express purpose without the need for the gerund.

For plus the object is a form we use when we want to say that we went, are going, or will go to a place for the purpose of getting, taking, or doing something. Because for is a preposition 8, it must be followed by a noun. Listen:

What did you do last weekend?

I drove to the mountains.

Why?

I went there for some fresh air.

In this sentence, the word for tells us why you went to the mountains: you wanted some fresh air. Notice that the object fresh air appears immediately after the word for.

We can express this same meaning using to and an infinitive. Listen:

I went to the mountains to get some fresh air.

Notice that the infinitive verb here is also followed by the object fresh air.

Let's listen to a couple talk about dinner:

I'm too tired to cook tonight.

Let's go out for Japanese food.

The second speaker is suggesting that they go to a Japanese restaurant because the first speaker is too tired to cook.

Here are some tips to help you remember how to use expressions of purpose.

Tip #1

Avoid putting the word for before an infinitive of purpose. Listen to three examples. Only one is correct. Do you know which it is?

One - I download podcasts every day for to practice my listening skills.

Two - I download podcasts every day to practice my listening skills.

Three - I download podcasts every day for practice my listening skills.

Write your answer in the comments section.

Tip #2

Avoid using the word to before a gerund. Choose the correct sentence of these three examples:

One - This tool is to weeding the garden.

Two - This tool is for weeding the garden.

Three - This tool is for to weeding the garden.

Write your answer in the comments section.

Words in This Story

phrase - n. a group of two or more words that express a single idea but do not usually form a complete sentence

podcast - n. a program, such as a music or news program, that is like a radio or television show but that is downloaded over the Internet

garden - n. an area of ground where plants, such as flowers or vegetables, are grown

download - v. to use the Internet to move or copy a file or program from one computer or device to another computer or device