Learn what the dictionary tells you about words.

Get Started Now!

Some compound words (like bus rapid transit, dog whistle, or identity theft) don’t appear on the drop-down list when you enter them into the search window. If a compound term doesn’t appear in the drop-down list, try entering the term into the search window and then hit the search button (instead of the “enter” key). Alternatively, begin searches for compound terms with a quotation mark.



The Usage Panel is a group of nearly 200 prominent scholars, creative writers, journalists, diplomats, and others in occupations requiring mastery of language. The Panelists are surveyed annually to gauge the acceptability of particular usages and grammatical constructions.

The Panelists



Go to our Crossword Puzzle Solver and type in the letters that you know, and the Solver will produce a list of possible solutions.



Check out the Dictionary Society of North America at



The online searchable American Heritage Dictionary includes definitions, pronunciations, etymologies, and feature notes. You can purchase the dictionary as an iOS or an Android app—or buy the deluxe printed edition.

The current “in-app purchase” version of the app is not compatible with iOS9 on iPads and is causing unexpected crashes. The update will be available soon. We apologize for this inconvenience.



Thousands of entries in the dictionary include etymologies that trace their roots back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

Indo-European Roots

Semitic Roots

Additional information is available in an expanded form in our Dictionary of Indo-European Roots.



Share your ideas for new words and new meanings of old words!

Start Sharing Now!


See word lists from the best-selling 100 Words Series!

Find out more!

that (thăt, thət)
pron. pl. those (thōz)
a. Used to refer to the one designated, implied, mentioned, or understood: What kind of soup is that?
b. Used to refer to the one, thing, or type specified as follows: The relics found were those of an earlier time.
c. Used to refer to the event, action, or time just mentioned: After that, he became a recluse.
2. Used to indicate the farther or less immediate one: That is for sale; this is not.
3. Used to emphasize the idea of a previously expressed word or phrase: He was fed up, and that to a great degree.
4. The one, kind, or thing; something: She followed the calling of that which she loved.
5. those Used to indicate an unspecified number of people: those who refused to join.
6. Used as a relative pronoun to introduce a clause, especially a restrictive clause: the car that has the flat tire.
a. In, on, by, or with which: each summer that the concerts are performed.
b. According to what; insofar as: He never knew her, that I know of.
adj. pl. those
1. Being the one singled out, implied, or understood: that place; those mountains.
2. Being the one further removed or less obvious: That route is shorter than this one.
1. To such an extent or degree: Is your problem that complicated?
2. To a high degree; very: didn't take what he said that seriously.
1. Used to introduce a noun clause that is usually the subject or object of a verb or a predicate nominative: "That contemporary American English is exuberantly vigorous is undeniable" (William Arrowsmith).
2. Used to introduce a subordinate clause stating a result, wish, purpose, reason, or cause: She hoped that he would arrive on time. He was saddened that she felt so little for him.
a. Used to introduce an anticipated subordinate clause following the expletive it occurring as subject of the verb: It is true that dental work is expensive.
b. Used to introduce a subordinate clause modifying an adverb or adverbial expression: will go anywhere that they are welcome.
c. Used to introduce a subordinate clause that is joined to an adjective or noun as a complement: was sure that she was right; persists in the belief that rates will rise soon.
4. Used to introduce an elliptical exclamation of desire: Oh, that I were rich!
at that
1. In addition; besides: lived in one room, and a small room at that.
2. Regardless of what has been said or implied: a long shot, but she just might win at that.
that is
To explain more clearly; in other words: on the first floor, that is, the floor at street level.

[Middle English, from Old English thæt; see to- in the Appendix of Indo-European roots.]

Usage Note: The standard rule requires that that should be used only to introduce a restrictive (or defining) relative clause, which identifies the entity being talked about; in this use it should never be preceded by a comma. Thus, in the sentence The house that Jack built has been torn down, the clause that Jack built is a restrictive clause identifying the specific house that was torn down. Similarly, in I am looking for a book that is easy to read, the restrictive clause that is easy to read tells what kind of book is desired. A related rule stipulates that which should be used with nonrestrictive (or nondefining) clauses, which give additional information about an entity that has already been identified in the context; in this use, which is always preceded by a comma. Thus, we say The students in Chemistry 101 have been complaining about the textbook, which (not that) is hard to follow. The clause which is hard to follow is nonrestrictive in that it does not indicate which text is being complained about; even if the clause were omitted, we would know that the phrase the textbook refers to the text in Chemistry 101. · Some people extend the rule and insist that, just as that should be used only in restrictive clauses, which should be used only in nonrestrictive clauses. By this thinking, which should be avoided in sentences such as I need a book which will tell me all about city gardening, where the restrictive clause which will tell me all about city gardening indicates which sort of book is needed. But this use of which with restrictive clauses is very common, even in edited prose. Moreover, in some situations which is preferable to that. Which can be especially useful where two or more relative clauses are joined by and or or: It is a philosophy in which ordinary people may find solace and which many have found reason to praise. Which may also be preferable when introducing a restrictive clause modifying a preceding phrase that contains that: We want to assign only that material which will be most helpful. · That can often be omitted in a relative clause when the subject of the clause is different from the word or phrase the clause refers to. Thus, one can say either the book that I was reading or the book I was reading. That can also be dropped when it introduces a subordinate clause: I think we should try again. That should be retained, however, when the subordinate clause begins with an adverbial phrase or anything other than the subject: She said that under no circumstances would she allow us to skip the meeting. The book argues that eventually the housing supply will increase. This last sentence would be ambiguous if that were omitted, since the adverb eventually could then be construed as modifying either argues or will increase. · There is a widespread belief, sometimes taught as correct usage, that only who and not that should be used to introduce a restrictive relative clause identifying a person. But that has been used in this way for centuries, going back to the Old English period, and has been used by the finest writers in English, as in "The man that once did sell the lion's skin / While the beast liv'd, was kill'd with hunting him" (Shakespeare). and "Scatter thou the people that delight in war" (King James Bible). In contemporary usage, who predominates in such contexts, but that is used with sufficient frequency to be considered standard, as in "The atoms in a diamond ... outnumber all the people that have ever lived or ever will" (Richard Dawkins). That also occurs idiomatically in reference to groups (where who would sound peculiar), as in "[She] had two sons, and settled into raising a family that soon included twin daughters" (David Freeman). See Usage Notes at doubt, this, whatever, which, who.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2015 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Have a promotional code?


Put the entire dictionary at your fingertips—anywhere, anytime!



This website is best viewed in Chrome, Firefox, Microsoft Edge, or Safari.