exchange From Middle English eschaunge, borrowed from Anglo-Norman eschaunge exchange 1.An act of exchanging or trading. All in all, it was an even exchange.an exchange of cattle for grain 2.A place for conducting trading. The stock exchange is open for trading. 3.A telephone exchange. 4.(telephony, US) The fourth through sixth digits of a ten-digit phone number (the first three before the introduction of area codes). The 555 exchange is reserved for use by the phone company, which is why it's often used in films.NPA-NXX-1234 is standard format, where NPA is the area code and NXX is the exchange. 5.A conversation. [quotations ▼]After an exchange with the manager, we were no wiser. 6.(chess) The loss of one piece and associated capture of another 1.(usually with "the") The loss of a relatively minor piece (typically a bishop or knight) and associated capture of the more advantageous rook 7.(obsolete) The thing given or received in return; especially, a publication exchanged for another. (Can we find and add a quotation of Shakespeare to this entry?) 8.(biochemistry) The transfer of substances or elements like gas, amino-acids, ions etc. sometimes through a surface like a membrane. 9.(finance) The difference between the values of money in different places. Exchange of one person or thing for another; reciprocal giving and receiving: (a) of prisoners of war; (b) of properties. Exchange of one kind or denomination of money for another; conversion of one kind of money into another for profit; an act of money-changing; the trade or authority of money-changing; (b) letter of eschaunge, a letter of credit. Exchange of goods, merchandise, or the like, by way of barter or sale; traffic in commodities of value; maken eschaunge(s; (b) fig. a bargain or agreement. Interchange; (b) replacement of one thing by another; substitution. Change, mutability; (b) transmutation.