There are Fundamental Elements in a simple contract - Offer and Acceptance.
There must be a valid offer, which must be clear, complete and final.
The words must be intended as an offer, as distinct from an invitation to treat, which is a first step in negotiations, a prelude to a firm offer being made by one of the parties. An article put in a shop window, or on a shelf in a self-service store, and marked with a price, does not constitute an offer.
Example : Pharmaceutical Society of Great Britain v Boots Cash Chemists (Southern) Ltd. [1953]. All E.R. 482.