Requirements must be analysed to obtain a satisfactory understanding of the customer's need and negotiated to establish an agreed set of consistent (unambiguous, correct, complete, etc) requirements.
(IEEE) (1) The process of studying user needs to arrive at a definition of a system, hardware, or software requirements. (2) The process of studying and refining system, hardware, or software requirements. See: prototyping, software engineering.
A basic review of what features a product will need to have, who the end users will be, how many of users will be using the system simultaneously, what hardware they will be using, what users will expect of the system and the general structure of the interface. Section 508 A list of protocols which government web sites are expected to follow in order to provide accessible pages to disabled users.