that.

Introducing a clause that is the object of a verb, especially a reporting verb or verb expressing belief, knowledge, perception, etc.

He told me that the book is a good read.

I believe that it is true.

Introducing a clause that is the subject of a verb, especially the ‘be’ verb or a verb expressing judgement, opinion, etc. As delayed subject.

It is almost certain that she will come.

It amazes me that people still believe this nonsense.

Introducing a clause that is the subject of a verb, especially the ‘be’ verb or a verb expressing judgement, opinion, etc. As direct subject.

That she will come is almost certain.

That people still believe this nonsense amazes me.

Introducing the complement of a mandative verb.

I insist that you come.

The boss ordered that the worker enter the room.

Introducing a clause that complements an adjective or passive participle.

I'm sure that you are right.

She is convinced that he is British.

Introducing a clause that complements an adjective or passive participle. Expressing a reason or cause: because, in that.

Be glad that you have enough to eat.

I was saddened that you felt so little for me.

Introducing a subordinate clause modifying an adverb.

Was John there? — Not that I saw.

How often did she visit him? — Twice that I saw.

Introducing a clause that describes the information content of a preceding reporting noun.

I heard a rumour that they got married.

Reports that he left the country are circulating.

Introducing — especially, but not exclusively, with an antecedent like so or such — a subordinate clause expressing a result, consequence, or effect.

The noise was so loud that she woke up.

The problem was sufficiently important that it had to be addressed.

Introducing a subordinate clause that expresses an aim, purpose, or goal (“final”), and usually contains the auxiliaries may, might, or should: so, so that, in order that.

He fought that others might have peace.

Introducing a premise or supposition for consideration: seeing as; inasmuch as; given that; as would appear from the fact that.

Introducing an exclamation expressing a desire or wish.

Oh that spring would come!

Introducing an exclamation expressing a strong emotion such as sadness or surprise.

That men should behave in such a way!

Oh that I'd never set eyes on him!

The (thing, person, idea, etc) indicated or understood from context, especially if more remote physically, temporally or mentally than one designated as “this”, or if expressing distinction.

That book is a good read. This one isn't.

That battle was in 1450.

The thing, person, idea, quality, event, action, or time indicated or understood from context, especially if more remote geographically, temporally or mentally than one designated as “this”, or if expressing distinction.

That's my car over there.

He went home, and after that I never saw him again.

The thing, person, idea, quality, event, action, or time indicated or understood from context, especially if more remote geographically, temporally or mentally than one designated as “this”, or if expressing distinction. Used to refer to a noun phrase or statement just made.

They're getting divorced. What do you think about that?

They gave me the book about whales. That I've not yet read.

The thing, person, idea, quality, event, action, or time indicated or understood from context, especially if more remote geographically, temporally or mentally than one designated as “this”, or if expressing distinction. Used to emphatically affirm or deny a previous statement or question.

The water is so cold! — That it is.

Would you like another piece of cake? — That I would!

In a relative clause, referring to a previously mentioned noun, as subject, direct object, indirect object, or object of a preposition; which, who.

I didn't see the car that hit me.

The CPR course that she took really came in handy.

Used in place of relative adverbs such as where or when; often omitted.

the place that [= where or to which] I went last year

the last time that [= when] I went to Europe

To a given extent or degree. Denoting an equal degree.

Here's the measurement – the ribbon must be that long, no longer and no shorter.

To a given extent or degree. Denoting ‘as much’, ‘no less’.

She said we waited for three hours, but I'm sure it wasn't that long.

It didn't seem like ten miles, but actually it was that far.

To a great extent or degree; very, particularly.

I was seen quite quickly — I didn't have to wait that long.

I did the run last year, and it wasn't that difficult.

To such an extent; so.

Ooh, I was that happy I nearly kissed her.

Something being indicated that is there; one of those.