law: Indian Contract Act, 1872 
  2. Interpretation-clause
  In this Act the following words and expressions are used in the
  
  following senses, unless contrary intention appears from the context:
  (a) When one person signifies to another his
  
  willingness to do or to abstain from doing anything, with a view to obtaining
  
  the assent of that either to such act or abstinence, he is said to make a
  
  proposal;
  (b) When the person to whom the proposal is
  
  made, signifies his assent thereto, the proposal is said to be accepted. A
  
  proposal, when accepted, becomes a promise;
  (c) The person making the proposal is called
  
  the "promisor", and the person accepting the proposal is called
  
  "promisee",
  (d) When, at the desire of the promisor, the
  
  promisee or any other person has done or abstained from doing, or does or
  
  abstains from doing, or promises to do or to abstain from doing, something,
  
  such act or abstinence or promise is called a consideration for the promise;
  (e) Every promise and every set of promises,
  
  forming the consideration for each other, is an agreement;
  (f) Promises which form the consideration or
  
  part of the consideration for each other, are called reciprocal promises;
  (g) An agreement not enforceable by law is
  
  said to be void;
  (h) An agreement enforceable by law is a
  
  contract;
  (i) An agreement which is enforceable by law
  
  at the option of one or more of the parties thereto, but not at the option of
  
  the other or others, is a voidable contract;
  (j) A contract which ceases to be enforceable
  
  by law becomes void when it ceases to be enforceable.