A book suggests that we should not interchange "so" and "so that". "So" means "therefore", and "so that" means "in order that". However, it seems to me that in many cases they don't actually have a difference. For example:

Alice got up at 5:00 A.M., so that she could drive her son to school.

If I substitute "so that" with "so", this sentence presents the exact same causal relation to me:

Alice got up at 5:00 A.M., so she could drive her son to school.

I must have missed something here, since English is my second language. Could somebody explain the difference?

  • I'm pretty sure we've had a question before on omitting "that"… Mar 6, 2011 at 9:53
  • 2
    It's okay to sometimes not mention that that as long as the meaning is clear. But I recommend keeping that for this sentence.
    – NVZ
    Jun 20, 2017 at 19:32
  • Similar without an answer How did so mean so that? Jun 20, 2017 at 19:57

6 Answers 6


If you are wondering about the difference between the two sentences, the first states Alice's reason for waking up early, while the second implies that she was successful in her intention.

This is not a distinction always observed by native speakers.

It is confusing, because "so" (when used as a conjunction) can mean "therefore" or can be an abbreviated form of "so that" (meaning "in order that.") In this way "so" has two distinct but similar meanings.

Subjectively I would say that using "so" in place of "so that" sounds a little informal and maybe a tiny bit childish, but is fine in conversational contexts.


They aren't interchangeable.

"so" is ambiguous, meaning both therefore and in order that, but "so that" isn't. Every occurrence of "so that" can be replaced with "so" without losing meanings, but not vice versa. For instance,

You are a bachelor, so you are a man.

"so" means therefore in this context. It doesn't make sense replacing "so" with "so that", the latter of which means "in order that". You are a bachelor in order to be a man?

Note: If two words can only be replaced with each other in some cases, your example being one of them, but not all, are they really interchangeable?


According to AHD

so ... conj. ...

  1. With the purpose that: I stayed so I could see you.

the use of 'so' instead of 'so that' when used to mean 'with the purpose that' is acceptable. They have a usage note:

Many critics and grammarians have insisted that so must be followed by that in formal writing when used to introduce a clause giving the reason for or purpose of an action:

He stayed so that he could see the second feature.

But since many respected writers use so for so that in formal writing, it seems best to consider the issue one of stylistic preference:

The store stays open late so (or so that) people who work all day can buy groceries.

Both so and so that are acceptably used to introduce clauses that state a result or consequence:

The Bay Bridge was still closed, so (or so that) the drive from San Francisco to the Berkeley campus took an hour and a half.


So that means "with the result that", "with the aim that", "in order that".

It was overgrown with brambles, so that she had difficulty making any progress.
They whisper to each other so that no one else can hear.

So means "to such a great extent", "extremely", "very much".
As conjunction, it means "and for this reason", "therefore", "and then"; it is also used to introduce a question, or a concluding statement.

She looked so pretty.
She likes it so.
She is not so foolish as to believe that.
It was still painful, so I went to see a specialist.
So, what is her name?
So that is the reason.
So you are free.

You cannot replace so with so that without changing the meaning of the sentence, or without changing the rest of the sentence.

  • Thank you for your answer, but I meant to use "so" as a conjunction, not an adverb.
    – evergreen
    Mar 6, 2011 at 5:30

Well for me, so and so that are different. In my opinion so is the same as therefore, and so that means in order to.

So so is making a conclusion, it is like you know already, or that something "can happen," according to your sentence; it is like the future predicted already. And therefore is somewhat like going to be, you are not sure if that thing can happen or it is like you cannot predict the future, yet because of the words "in order to," it is like telling me to prevent things that you do not want to happen in a sentence.

Using so that is ignoring one thing, you did this because you do not want that to happen, not like the word so, you are already knowing what is going to happen next, that is why you did this, because you want that thing to happen.


In this context, 'So' and 'so that' both mean 'as a result' of the preceding clause. The difference is 'SO THAT' refers to a condition that can take place as a result of planned action, while 'SO' implies a condition can take place because the situation allows it.

'SO' - The situation was that Alice happened to wake up early. It was alright if she overslept. She didn't plan to wake up early but she did. Because she was already up, it now meant that she was in time to drive her son to school.

'SO THAT' means Alice woke up early as planned. She probably set an alarm clock for 5am or kept awake all night because she knew she should not oversleep. The reason for her to wake up early was to be able to drive her son to school.

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