Explanatory Notes Attributive Nouns

Capitalization Index   Etymology

The italicized label  often attrib placed after the functional label  n indicates that the noun is often used as an adjective equivalent in attributive position before another noun:
¹ air ...  n, often attrib
com·put·er ...  n, often attrib
Examples of the attributive use of these nouns are  air traffic and  computer printout.

While any noun may occasionally be used attributively, the label  often attrib is limited to those having broad attributive use. This label is not used when an adjective homograph (as  iron or  paper ) is entered. And it is not used at open compounds (as  X ray ) that may be used attributively with an inserted hyphen (as in  X-ray therapy ).