Real Dictionary

demand
countable noun: A demand is a firm request for something.
uncountable noun: If you refer to demand, or to the demand for something, you are referring to how many people want to have it, do it, or buy it.
verb: If one thing demands another, the first needs the second in order to happen or be dealt with successfully.
verb: If you demand something such as information or action, you ask for it in a very forceful way.

demand in American English
to ask for boldly or urgently
intransitive verb: to make a demand; inquire; ask
noun: the act of demanding
transitive verb: to ask for with proper authority; claim as a right

demand in British English
to request peremptorily or urgently
noun: an urgent or peremptory requirement or request

demand in Electrical Engineering
noun: Demand is the rate at which electric energy is delivered to or by a system, part of a system, or a piece of equipment.