Categories, Section 1, Part 4

Expressions which are in no way composite signify substance, quantity,
quality, relation, place, time, position, state, action, or affection.
To sketch my meaning roughly, examples of substance are 'man' or 'the
horse', of quantity, such terms as 'two cubits long' or 'three cubits
long', of quality, such attributes as 'white', 'grammatical'. 'Double',
'half', 'greater', fall under the category of relation; 'in a the
market place', 'in the Lyceum', under that of place; 'yesterday',
'last year', under that of time. 'Lying', 'sitting', are terms indicating
position, 'shod', 'armed', state; 'to lance', 'to cauterize', action;
'to be lanced', 'to be cauterized', affection.

No one of these terms, in and by itself, involves an affirmation;
it is by the combination of such terms that positive or negative statements
arise. For every assertion must, as is admitted, be either true or
false, whereas expressions which are not in any way composite such
as 'man', 'white', 'runs', 'wins', cannot be either true or false.