Merriam-Webster Collegiate Dictionary - that

 I. pronoun  (plural those)  Etymology: Middle English, from Old English th?t, neuter demonstrative pronoun & definite article; akin to Old High German daz, neuter demonstrative pronoun & definite article, Greek to, Latin istud, neuter demonstrative pronoun  Date: before 12th century  1.  a. the person, thing, or idea indicated, mentioned, or understood from the situation ~ is my father  b. the time, action, or event specified after ~ I went to bed  c. the kind or thing specified as follows the purest water is ~ produced by distillation  d. one or a group of the indicated kind ~'s a cat — quick and agile  2.  a. the one farther away or less immediately under observation or discussion those are maples and these are elms  b. the former one  3.  a. — used as a function word after and to indicate emphatic repetition of the idea expressed by a previous word or phrase he was helpful, and ~ to an unusual degree  b. — used as a function word immediately before or after a word group consisting of a verbal auxiliary or a form of the verb be preceded by there or a personal pronoun subject to indicate emphatic repetition of the idea expressed by a previous verb or predicate noun or predicate adjective is she capable? She is ~  4.  a. the one ; the thing ; the kind ; something, anything the truth of ~ which is true the senses are ~ whereby we experience the world what's ~ you say  b. plural some persons those who think the time has come  II. conjunction  Date: before 12th century  1.  a.  (1) — used as a function word to introduce a noun clause ~ is usually the subject or object of a verb or a predicate nominative said ~ he was afraid  (2) — used as a function word to introduce a subordinate clause ~ is anticipated by the expletive it occurring as subject of the verb it is unlikely ~ he'll be in  (3) — used as a function word to introduce a subordinate clause ~ is joined as complement to a noun or adjective we are certain ~ this is true the fact ~ you are here  (4) — used as a function word to introduce a subordinate clause modifying an adverb or adverbial expression will go anywhere ~ he is invited  b. — used as a function word to introduce an exclamatory clause expressing a strong emotion especially of surprise, sorrow, or indignation ~ it should come to this!  2.  a.  (1) — used as a function word to introduce a subordinate clause expressing purpose or desired result cutting down expenses ~ her son might inherit an unencumbered estate — W. B. Yeats  (2) — used as a function word to introduce a subordinate clause expressing a reason or cause rejoice ~ you are lightened of a load — Robert Browning  (3) — used as a function word to introduce a subordinate clause expressing consequence, result, or effect are of sufficient importance ~ they cannot be neglected — Hannah Wormington  b. — used as a function word to introduce an exclamatory clause expressing a wish oh, ~ he would come  3. — used as a function word after a subordinating conjunction without modifying its meaning if ~ thy bent of love be honorable — Shakespeare  III. adjective  (plural those)  Date: 12th century  1.  a. being the person, thing, or idea specified, mentioned, or understood  b. being the one specified — usually used for emphasis ~ rarity among leaders ~ brother of yours  c. so great a ; such  2. the farther away or less immediately under observation or discussion this chair or ~ one  IV. pronoun  Etymology: Middle English, from Old English th?t, neuter relative pronoun, from th?t, neuter demonstrative pronoun  Date: before 12th century  1. — used as a function word to introduce a restrictive relative clause and to serve as a substitute within ~ clause for the substantive modified by the clause the house ~ Jack built I'll make a ghost of him ~ lets me — Shakespeare  2.  a. at which ; in which ; on which ; by which ; with which ; to which each year ~ the lectures are given  b. according to what ; to the EXTENT OF WHAT — USED AFTER A NEGATIVE HAS NEVER BEEN HERE ~ I KNOW OF  3.  a. archaic ~ which  b. obsolete the person who Usage:  That, which, who: In current usage ~ refers to persons or things, which chiefly to things and rarely to subhuman entities, who chiefly to persons and sometimes to animals. The notion ~ ~ should not be used to refer to persons is without foundation; such use is entirely standard. Because ~ has no genitive form or construction, of which or whose must be substituted for it in contexts ~ call for the genitive. Usage:  That, which: Although some handbooks say otherwise, ~ and which are both regularly used to introduce restrictive clauses in edited prose. Which is also used to introduce nonrestrictive clauses. That was formerly used to introduce nonrestrictive clauses; such use is virtually nonexistent in present-day edited prose, though it may occasionally be found in poetry.  V. adverb  Date: 13th century  1. to such an extent a nail about ~ long  2. very, extremely — usually used with the negative did not take the festival ~ seriously — Eric Goldman