that: [OE] That is a very ancient word, going right back to prehistoric Indo-European *tad (source also of Greek tó ‘the’ and Russian tot’, ta, to ‘that’). Its original function in English was as the neuter form of a demonstrative pronoun. This came to be used as the definite article (modern English the), but as the grammatical gender system began to break down in the early Middle English period, that broke away from the definite article and began to be used as a demonstrative adjective. Its use as a relative pronoun goes back to the Old English period. => the
that (pron.)
Old English þæt, "that, so that, after that," neuter singular demonstrative pronoun ("A Man's a Man for a' that"), relative pronoun ("O thou that hearest prayer"), and
demonstrative adjective ("Look at that caveman go!"), corresponding to masc. se, fem. seo. From Proto-Germanic *that, from PIE *tod-, extended form of demonstrative pronominal base *-to- (see -th (1)). With the breakdown of the grammatical gender system, it came to be used in Middle English and Modern English for all genders. Germanic cognates include Old Saxon that, Old Frisian thet, Middle Dutch, Dutch dat "that," German der, die, das "the."
Generally more specific or emphatic than the, but in some cases they are interchangeable. From c. 1200 opposed to this as indicating something farther off. In adverbial use ("I'm that old"), in reference to something implied or previously said, c. 1200, an abbreviation of the notion of "to that extent," "to that degree." Slang that way "in love" first recorded 1929. That-a-way "in that direction" is recorded from 1839. "Take that!" said while delivering a blow, is recorded from early 15c.
双语例句
1. A miracle is something that seems impossible but happens anyway.
奇迹就是看似不可能，却发生了。
来自电影《黑衣人3》
2. If you wait, all that happens is that you get older.
如果你等待，发生的只有变老。
来自金山词霸 每日一句
3. When life gets hard and you want to give up, remember that life is full of ups and downs, and without the downs, the ups would mean nothing.
当生活很艰难，你想要放弃的时候，请记住，生活充满了起起落落，如果没有低谷，那站在高处也失去了意义。
来自
4. Eventually, you'll learn to cry that on the inside.
终有一天，你会学会让泪往心里流。
来自美剧《破产姐妹》
5. Success is not final, failure is not fatal: it is the courage to continue that counts.--Winston Churchill