concept which corresponds to only one object
NOTE 1 Examples of individual concepts are 'Saturn', 'the Eiffel Tower'.
NOTE 2 Individual concepts are usually represented by appellations.
[ISO 1087-1:2000, definition 3.2.2]
concept which corresponds to two or more objects which form a group by reason of common properties
NOTE Examples of general concepts are planet, tower.
[ISO 1087-1:2000, definition 3.2.3]