Quantities in radiation protection, functions and roles

An apparently complex situation has been caused in recent years by the definition of a number of new quantities in radiation protection. The complexity is reduced if it is recognised that each quantity is suitable for one of three roles; risk estimation, operational measurement or primary standardisation. This understanding leads to an appreciation of the required inter-relationships between the values of the quantities. The recently introduced quantities, their roles, and the requirements of their inter-relationships are discussed. (author)