The period of time which a product can be stored, under
specified conditions, and remain in a suitable condition for
consumption. Pharmaceutical companies estimate the shelf life (and then
expiration date) of a drug to determine the amount of time the drug is
at acceptable levels of potency, color, etc that are agreed with
government health authorities.

See
also:
National Institute for
Health and Clinical Excellence (NICE)
Association of the British Pharmaceutical
Industry (ABPI)