We read about these three classes of sentences. For example,

  • It is too hot to go out without an umbrella. (Simple)
  • It is so hot that we cannot go out without an umbrella. (Complex)
  • It is very hot and so we cannot go out without an umbrella. (Compound)

My teacher then (around a decade back) pointed out the "too-to" structure in simple sentences and a "so-that" structure in complex sentences. He added that casual sentences like I am so busy or I am too tired are wrong and in each of those cases, we need a very, as in, I am very busy or I am very tired. His logic was that so or to need a that or to for meaningful completion, going by the examples above.

Is he correct? Does modern English deem I am so busy to be suitable or valid in formal contexts (say in written English or the English taught at schools)? Is It is too/so hot and so we cannot go out without an umbrella a valid compound sentence?


4 Answers 4


I think it very likely that your English teacher was giving you ‘baby rules’: the sort of very broad rules you give a child (or learner) to prevent it from hurting itself before it is old enough (or knowledgeable enough) to understand subtle qualifications.

  • In the case of too, your teacher was probably ‘protecting’ you from a very common learner’s error: using too as a simple intensive, equivalent to very.

    The ‘grown-up’ rule is that although it is quite true that too almost always involves a comparison of the sort you have in too hot to go out, this does not mean that the comparison must actually be expressed in every sentence in which you use too. The benchmark against which you are measuring may be entirely clear from the context.

    Do you want to go for a walk?
    No, thanks, it’s too hot.

  • In the case of so, your teacher was probably trying to keep you from using intensive so in an inappropriate register. This use of so is colloquial and almost never found in formal or semi-formal registers such as you are typically called upon to employ in school essays. But in conversation (or dialogue, if you are writing fiction or a play or a script) it’s perfectly acceptable:

    It is so hot today!

Such rules are pedagogically useful: they keep you focused on what you must learn and keep you from being distracted by all the million-and-one-things you might learn. But in language (as in pretty much everything else), once you reach a certain level of competence you may safely ignore classroom rules and instead follow the practice of writers and speakers you admire.


It is too hot to go out without an umbrella.

is OK.

It is so hot that we cannot go out without an umbrella.

is also OK, but it intensifies hot, so you are meaning something like "it is excessively hot".


It is very hot and so we cannot go out without an umbrella.

Here, the two phrases It is very hot and so we cannot go out without an umbrella don't seem related and in any case it sounds strange. To link the phrases better, you could say:

It is very hot, therefore we cannot go out without an umbrella.

I like therefore better than so, as it clearly indicates the second phrase is a result of the first one.


As far as I know, both "I am so busy" and "It is too/so hot and so we cannot go out without an umbrella" are grammatical.

In the former "so" is an intensifier, however to avoid in academic writing.

In the latter either "so" or "too" are intensifiers and the second "so" serves as a linking adverb; depending on the context you can avoid the "and" there: "It is too/so hot. So we cannot go out without an umbrella."

  • snail, I'm sure you are right, but I like to give a little contribution to ELL as an answerer, too, even if I'm not a competent speaker. Thank you for your helpful comment.
    – user114
    Commented Apr 3, 2013 at 22:18

So means also "very; extremely." It is used, for example, in sentences similar to the following ones.

I am so glad to see you.
Their attitude is so very English.
He sat there ever so quietly.

All those sentences are grammatically acceptable.

  • Can you provide some more detail? Were they ungrammatical at some point in time in the past, at least in formal writing?
    – Sultan
    Commented Apr 3, 2013 at 22:16
  • 1
    @Sultan So has been an intensifier in English for over a thousand years. It may not be appropriate in formal writing, but it isn't ungrammatical.
    – user230
    Commented Apr 3, 2013 at 22:32
  • @Sultan, since 1980 grammarians use the term "pro-forms" to call "so" and other various words that substitute for others in a text. So, what past are you referring to? Maybe before 1985, that "so" usage was ungrammatical, but snail says no, though.
    – user114
    Commented Apr 3, 2013 at 22:35
  • @snailplane: If you make that distinction between grammaticality and appropriateness, it is the latter about which I want to know.
    – Sultan
    Commented Apr 3, 2013 at 22:35
  • @Sultan, it is not snail that make that distinction, but language and vocabulary. We all use English dictionary and so we can undarstand one with each other.
    – user114
    Commented Apr 3, 2013 at 22:37

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