As a general rule, the English language aims to avoid repetition.

That's why, on Everyday Grammar, we talk about ways to shorten sentences – in spoken English and in some forms of writing. Shortened speech helps us avoid restating what we, or others, have just said.

For example, my sister and I just exchanged text messages that demonstrate how to say something in only a few words. I'll share our messages with you.

She would like to use something of mine, so she wrote: Hey, do you have an extra air bed? Some friends are visiting this weekend.

I responded: I think so!! I'll check tonight.

In my text, the word "so" shortened a longer sentence. "I think so" means "I think that I have an extra air bed." When we use "so" this way, we are replacing a group of words known as a that-clause.

On a past Everyday Grammar program, we introduced this idea. Today, we will look at the grammar in steps.

Step 1: What is a clause?

The first step is to understand what a clause is. A clause is a part of a sentence with its own subject and verb.

Many sentences in English contain two or more clauses. Imagine I wrote a longer text to reply to my sister:

I think that I have an extra air bed.

This sentence has two clauses – a main clause and supporting clause. The main clause is "I think." Its subject is "I" and verb is "think."

The main clause is joined to a second clause that gives us more information – in this case, a that-clause.

"That I have an extra air bed" is the that-clause. It begins with the word "that" and has its own subject and verb. Its subject is "I" and verb is "have."

Step 2: Replacing that-clauses

Now let's move to step two – how to replace that-clauses with "so."

There are a few kinds of that-clauses in English, and not all can be replaced with "so." We mostly do it when sentences follow the structure subject + verb + that-clause.

This kind of that-clause is a noun clause. But remembering that term is not important for today's lesson.

We replace that-clauses with "so" only after a limited number of verbs, including:

think, believe, hope, guess, suppose, assume, imagine, know, say and tell

Most of these verbs (except "say" and "tell") can express uncertainty or an opinion. "Say" and "tell" are reporting verbs, which we can use to talk about what someone else said.

Step 3: Hearing examples

All of this will become clearer in step three – hearing examples.

Let's now listen to a few.

I recently asked a friend if she'd won an award for small businesses in New York. Her response was something like this:

I haven't gotten an answer yet. But I really hope so!!

Later, she found out that she was a winner!

Our next example has a reporting verb. Notice that there's just one speaker:

I'm not sure if Alfredo's coming to the watch party. He said so. But it's after 5pm and I haven't seen him.

We can shorten that-clauses in our own speech, not just in responses.

And this last one answers a suggestion:

Should we wait until tomorrow to go hiking?I suppose so. It's close to sunset so the bugs will be out now.

Step 4: The missing "that"

OK, onto step four.

I imagine this step will be a huge help as you continue studying English.

When native speakers say or write things, we often leave out the word "that" in that-clauses. In fact, I did it a few sentences ago. Did you catch it? Here's a clue: I said "I imagine..."

Recognizing missing "thats" will help you understand and write English better.

Step 5: Negative forms

Now for step five: negative forms. When we replace that-clauses with "so" in negative sentences, we do it differently for different verbs.

After the verbs "think," "believe," "say," and some others, we make the negative this way:

I don't suppose so.The witness didn't say so.Rachel doesn't think so.

But, after the verbs "guess" and "hope," we form the negative without the verb "do" and put "not" at the end, like this:

I guess not.We hope not.

We do not say, "I don't guess so" or "We don't hope so."

What you can do

Wow, we covered a lot today! Don't try to remember it all. Instead, look and listen for signals of that-clauses anywhere that English is used.

You can start by paying attention when people use the verbs "think," "believe," "guess" and "hope" in positive or negative form. Then, ask yourself if the speaker or writer used a full that-clause, left out the word "that" or replaced the clause completely with "so."

For instance, at a restaurant or market, a worker might ask a customer, "Would you like anything else today?" The customer might respond, "I don't think so, thanks."

And, I think we are done for today, too!

Alice Bryant wrote this story for Learning English. Kelly Jean Kelly was the editor.

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