group of objects with common properties
EXAMPLE "telephone", "desk", "chair", "ball bearing", and "tennis ball" are classes.
quality or feature of an object
anything perceivable or conceivable
NOTE 1 Objects may be material (e.g. an engine, a sheet of paper, a diamond), immaterial (e.g. conversion ratio, a project plan) or imagined (e.g. a unicorn).
[ISO 1087-1:2000, definition 3.1.1]
NOTE 2 The radial flow centrifugal pump with serial number AX52386 is an object. Its general structure is defined by the radial flow centrifugal pump class.