In the following brief descriptions the five predicables are designated:
(1) This (species)
rectangle is a (genus)
parallelogram with (differentia)
four right angles its longer sides being (accident)
ten inches.
(2) This (species)
man is a (differentia)
rational (prox. genus)
biped with the (property)
power of locomotion and a (accident)
ruddy complexion.
(3) A (species)
trigon is a (genus)
polygon of (differentia)
three sides and (property)
three angles, (accident)
the sum of the angles being equal to two right angles.
3. THE NATURE OF A DEFINITION.
It will be remembered that an individual notion is a notion of a single thing or attribute, while a general notion is a notion of a class of things or a group of attributes. A term which represents an individual notion is known as a singular term, while a term which stands for a general notion is referred to as a general term.
One may explain the meaning of a singular term which stands for one thing by enumerating its various attributes. For example, such attributes as a piercing bark, a yellow color, intelligent, companionable, a strong liking for sweetmeats, explain the meaning of the singular term “Fido.” Likewise we may explain the meaning of a general term by enumerating its attributes. To illustrate:power of speech, rationality, ability to laugh, etc., explain the meaning of the general term man. The explanation of the singular term fits only Fido. There is probably no other dog in the world just like Fido. But the explanation of the general term man may be applied to all men.
A brief enumeration of attributes which may be applied to a class of things often takes the form of a definition. The word definition comes from the word definire, meaning to limit or fix the bounds of.
A definition, then, consists of the enumeration of such attributes as distinguish a term from all other terms. In this sense it would seem that the singular term Fido, as well as the general term man, admits of definition, but it is usual for logicians to confine definition to the general term. Singular terms may be described; general terms, defined.
A DEFINITION OF DEFINITION.