1. The term 'opposite' is applied to contradictories, and to contraries, and to relative terms, and to privation and possession, and to the extremes from which and into which generation and dissolution take place; and the attributes that cannot be present at the same time in that which is receptive of both, are said to be opposed, - either themselves of their constituents. Grey and white colour do not belong at the same time to the same thing; hence their constituents are opposed.
2. The term 'contrary' is applied: -
3. (1) to those attributes differing in genus which cannot belong at the same time to the same subject,
4. (2) to the most different of the things in the same genus,
5. (3) to the most different of the attributes in the same recipient subject,
6. (4) to the most different of the things that fall under the same faculty,
7. (5) to the things whose difference is greatest either absolutely or in genus or in species.
8. The other things that are called contrary are so called, some because they possess contraries of the above kind, some because they are receptive of such, some because they are productive of or susceptible to such, or are producing or suffering them, or are losses or acquisitions, or possessions or privations, of such. Since 'one' and 'being' have many senses, the other terms which are derived from these, and therefore 'same', 'other', and 'contrary', must correspond, so that they must be different for each category.
9. The term 'other in species' is applied to things which being of the same genus are not subordinate the one to the other, or which being in the same genus have a difference, or which have a contrariety in their substance; and contraries are other than one another in species (either all contraries or those which are so called in the primary sense), and so are those things whose definitions differ in the infima species of the genus (e.g. man and horse are indivisible in genus, but their definitions are different), and those which being in the same substance have a difference. 'The same in species' has the various meanings opposite to these.