That

[Casiopea]

Originally Posted by jack

Oh, interesting.

How would people know if it is omitted or not? I see this on the tv somtimes too and I don't understand why sometimes it is plural or whatsoever.

Sam: I like dogs.
Pat: I like cats.
Max: I like both.

Max uses the word 'both' to refer to 'dogs' and 'cats'. Max could have said, "I like both cats and dogs", but since those nouns have already been mentioned by Pat and Sam, Max feels no need to say them again, so Max leaves them out and says, 'both'. Note that, 'both' always means, two, so the verb will always be plural.

[jack]

Thanks.

Both words function as the subject. (OK)

Are these correct? If not why?
1. Both words function as subject.
2. Both words function as a subject.
3. Both words function as subjects.

[Casiopea]

Originally Posted by jack

2. Both words function as a subject.
3. Both words function as subjects.

Both 'John' and 'Max' function as the subject of this specific sentence.
Both 'John' and 'Max' function as subjects (of two separate sentences).

[jack]

Are these correct? What do these mean?
1. I am not going to buy anything you recommend.
2. I am not going to buy anything that you recommend.

3. The only way you can learn is by asking questions.
4. The only way that you can learn is by asking questions.

When would I use 'that'? How do I know when do I need it for sentences like these?

Is this question correct?
5. How do I know when do I need it for sentences like these? (The bold part sounds kind of strange to me, how can I repair it?)

[Casiopea]

The underlined portions modifies the noun 'anything' and the noun 'way', respectively. The word 'that' is a conjunction: It joins 'anything' with 'you recommend', and it joins 'way' with 'you can learn'. If we omit 'that', the sentence will remain grammatical because the underlined portion functions as an adjective:

1. I am not going to buy anything you recommend. (OK)
2. I am not going to buy anything that you recommend. (OK)
3. The only way you can learn is by asking questions. (OK)
4. The only way that you can learn is by asking questions. (OK)

5. How do I know when do I need it for sentences like these? (Not OK; delete 'do').

[jack]

Thanks.

[Casiopea]

Originally Posted by jack

Oh, interesting.

How would people know if it is omitted or not? I see this on the tv somtimes too and I don't understand why sometimes it is plural or whatsoever.

Well, firstly, both is a quantifier. It modifies a noun. That is, it always needs a noun, so if it occurs by itself, we know there's a noun there but that the speaker has omitted it. Secondly, "Both" refers to two things/people, so it's always plural, and that's why its verb is also plural:

EX: Both function... (OK)
EX: Both words function... (OK)

So you see, even if we omit the noun 'words' the verb is still plural because 'Both' is plural.

[jack]

So you see, even if we omit the noun 'words' the verb is still plural because 'Both' is plura

Thanks. This is useful.

What do these mean?
1. What's the top speed you have gone with your bike? (Is is correct without 'that'?)
2. What's the top speed that you have gone with your bike?

[Casiopea]

Originally Posted by jack

Thanks. This is useful.

What do these mean?
1. What's the top speed you have gone with your bike? (Is is correct without 'that'?)
2. What's the top speed that you have gone with your bike?

You're welcome.

Both are OK with or without 'that'.

[jack]

Both are OK with or without 'that'.

1. Do you think that she was going to go tonight? (Is 'that' referring to 'that thing'?)
2. Do you think she was going to go tonight? (Why doesn't it matter if I leave out 'that'?

so only one or the other is possible as subject, not both.

How come it is not like this?
1. So only one or the other is possible as a subject, not both.
2. So only one or the other is possible as subjects, not both.
3. So only one or the other is possible as subject, not both. (Why is this okay without an article?)