Demand means to state a need, requirement or entitlement, such as demanding payment or performance under a contract. In legal terms, demand also refers to the amount requested by a plaintiff during negotiations to settle a lawsuit or the amount of damages requested by the plaintiff as stated in their complaint. The demand in a complaint is governed by state laws, which vary by state. The plaintiff must generally ask for the type of damages sought, although not necessarily a dollar amount, in the complaint's demand or waive the right to recovery for that item of damages. Demand may also refer to a note payable at any time a request to pay is made, which is then said to be "payable on demand".
In the general sense, the term may describe any letter from one party to another demanding that the second party either take a particular action or not take that action. It is often a preliminary step to commencing court proceedings. The simplest letter of demand is for payment of money.