"[A] verbal operant in which the response is reinforced by a characteristic consequence and is therefore under the functional control of relevant conditions of deprivation or aversive stimulation" -- B.F. Skinner
Mand is a verbal behavior term, used in applied behavior analysis. It's closely related to the words "demand" and "command", and generally speaking, it means the same thing. A mand is a request, a demand, a statement of need, an order, and etc. The OED defines it concisely as "An utterance aimed at producing an effect or result".
Let's sort through Skinner's techno-babble.
- "relevant conditions of deprivation or aversive stimulation"
I step on your foot.
- ""[A] verbal operant"
You say "get off my foot!" (That is the mand).
- "a characteristic consequence"
I get off your foot.
- "the response is reinforced"
You learn that "get off my foot!" is a good thing to say (a good mand) when I step on your foot.
Mands are one of the first steps in learning language. The child is encouraged to learn language in response to its greatest desires; the mastering of mands can help you quench thirst, get fed, and call Mommy to your side. Mands also help language learning by pairing positive results with language use, spurring further language use in areas apart from manding.
Mands have a effective feedback loop in that they are reinforced in direct proportion to how relevant they are to the situation. If I want a cookie, and ask for a cookie, and get a cookie, then my mand has been successfully reinforced. If I'm full, and ask for a cookie, and get a cookie, then my mand has not been reinforced (not effectively, anyway). The usage of mands should auto-correct to match the needs of the one learning the mands.
Mands are of interest to behavioral psychologists and speech therapists. Other things in the same vein and of interest to the same people are Tact, Echoic, Intraverbal, Receptive repertoire, and Imitation.