Phrases which, as a unit, act as a noun; and whose heads are nouns or pronouns. English noun phrases can include (among many other possibilities) articles or determiners such as "the" and "a" and one or more adjectives or other nouns used attributively followed by the head noun itself.
Some background. Functional requirement of a web service is concerned with the correctness of the web service's function — say, the service will always return a number that is less than two. The ...