that

pronoun & determiner (plural those)

1》 used to identify a specific person or thing observed or heard by the speaker.

    ↘referring to the more distant of two things near to the speaker.

2》 referring to a specific thing previously mentioned or known.

3》 used in singling out someone or something with a particular feature.

4》 informal, chiefly Brit. expressing strong agreement with something just said: ‘He's a fussy man.’ ‘He is that.’

5》 [as pronoun] (plural that) used instead of which, who, when, etc. to introduce a defining clause, especially one essential to identification.

adverb to such a degree.

↘[with negative] informal very: he wasn't that far away.

conjunction

1》 introducing a subordinate clause.

2》 literary expressing a wish or regret.

Phrases

and all that (or and that) informal and so on.

(just) like that informal instantly or effortlessly.

that is (or that is to say) a formula introducing or following an explanation or further clarification.

that said even so.

that's that there is nothing more to do or say about the matter.

Origin

OE thæt, nominative and accusative singular neut. of se 'the', of Gmc origin.

Usage

When is it correct to use that and when should you use which? The general rule is that, when introducing clauses that define or identify something (known as restrictive relative clauses), it is acceptable to use either that or which: a book which aims to simplify scientific language or a book that aims to simplify scientific language. However, which, but never that, should be used to introduce clauses giving additional information (non-restrictive relative clauses): the book, which costs £15, has sold a million copies not the book, that costs £15, has sold a million copies.