Negative Infinitive of Purpose

What the infinitive of purpose is

An infinitive of purpose is a to + verb phrase that tells us why someone does something. It answers the question “why?”

• I went to the shop to buy milk.
• She studies hard to get good marks.
• He called to ask for help.

The main verb can be in any tense. The infinitive stays the same: I exercise every day to stay healthy. I went to university to get a degree.

How to make it negative

To say what you want to avoid, put not before to, usually with a longer purpose phrase:

Both mean “because I wanted to avoid this.” In order not to tends to sound a little more formal than so as not to, though the meaning is the same.

Why “not to” alone can be unclear

A bare not to before a verb is sometimes used, but it can be ambiguous or can look like a different structure. Compare:

• I told him not to eat the cake. This is an instruction that was reported: the thing I told him was “don’t eat the cake”. The not to belongs to the verb told, and it is not really a purpose.
• I told him so as not to upset him later. Here, the purpose of telling him is to avoid upsetting him.

For this reason, in order not to and so as not to are the clearest ways to show negative purpose, especially in writing.

Examples of negative infinitives of purpose

• She wore a coat in order not to catch a cold.
• We left early so as not to miss the train.
• He wrote the number down in order not to forget it.
• They whispered so as not to disturb the class.
• I double-checked the address so as not to send the parcel to the wrong place.
• She kept her phone on silent in order not to be distracted.
• The team worked carefully so as not to damage the equipment.
• He took notes in order not to lose track of the discussion.
• We saved money so as not to run out before the end of the month.
• You should stretch first so as not to hurt yourself.

Formal and informal choices

• To + infinitive (positive): neutral and very common. I called to ask.
• In order to / in order not to: slightly more formal.
• So as to / so as not to: similar in meaning; common in both speech and writing.

There is no neutral “short” negative that works as simply as the positive to. That is why learners are generally advised to use in order not to or so as not to for negative purpose.

When the subjects differ: so that

The infinitive of purpose works when the subject of the main verb is also the person doing the infinitive action. If they are different, use a so that clause. (For reasons rather than purposes, see because sentences examples.)

• I went to the library to study. (I went, and I studied.)
• I went to the library so that John could study. (I went, but John studied.)

For negative purpose, so that is usually followed by a negative verb with would, could, or won’t:

• She closed the door so that the noise wouldn’t wake the baby.
• I’ll write it down so that you won’t forget.

In order that is also possible in very formal writing.

Common mistakes

These errors also appear in sentence correction exercises.

1. Using for + verb. Incorrect: I went to the shop for buy bread. Correct: I went to the shop to buy bread.
2. Misplacing not. Incorrect: He spoke quietly to not wake them. Correct: He spoke quietly so as not to wake them. (Split infinitives like “to not wake” are common in speech, but the in order not to and so as not to forms are clearer.)
3. Using the infinitive when the subjects are different. Incorrect: I opened the window to the room cool down. Correct: I opened the window so that the room would cool down.
4. Mixing the patterns. Avoid blends such as so in order not to. Choose one full pattern, in order not to or so as not to, and keep it intact.

Purpose of or purpose for?

Both can be correct, but they work with different structures. We often say the purpose of something: The purpose of the meeting is to agree a plan. We use for when naming the use, such as a tool for cutting wood. After either, a to + verb or an -ing form can follow, depending on the phrase.

Types of infinitive in English

The infinitive is often described in terms of forms:

• Simple (present) infinitive: to write
• Continuous infinitive: to be writing
• Perfect infinitive: to have written
• Perfect continuous infinitive: to have been writing

There is also the bare infinitive (without to), used after modal verbs: She can swim. The infinitive of purpose is one use of the simple to-infinitive.

Frequently asked questions

What is the infinitive of purpose? It is a to + verb structure that explains the reason for an action.

How do I make it negative? Use in order not to or so as not to before the verb.

Can I use “for” before a verb to show purpose? No. Use to + verb: I came to help, not I came for help you.

What if the subject changes? Use so that, as in I spoke quietly so that he wouldn’t hear.