This International Standard defines the terms to be used in the field of measurement of fluid flow in closed conduits, and gives the corresponding Symbols. lt has been found necessary to exclude terms which come under the following categories: a) terms which are self-evident; b) terms which do not apply specifically to this field, in particular those referring more specifically to flow in open channels (see ISO 772); c) terms referring to very specific methods of measurement which cannot be the subject of standardization.