You may know that connotation of a term consists of common and essential attributes shared by all the objects denoted by the term. A connotative definition identifies the meaning of a term by providing a synonymous linguistic expression.
A connotative definition is a verbal definition. The definition of ‘triangle’ as ‘a plane figure enclosed by three straight lines’ is an example of connotative definition. In such definitions, the word or expression being defined is called the definiendum, and the expression that states the definition is called the definiens.
Thus, above example, ‘triangle’ is the definiendum, while ‘a plane figure enclosed by three straight is the definiens. The definiens and the definiendum are synonymous expressions and both the same meaning.
An effective and popular method of providing connotative definitions for general terms is by stating their genus and differentia. Classical logicians have developed this method in great. The basic procedure involved in providing this kind of definition is as follows we begin by identifying a wider class (the genus) of which the term is a subclass (species); then we specify the distinctive features (the differentia) that set the members of this subclass apart from all the other things belonging to other subclasses within that wider class.
Our definition of ‘triangle’ stated above followed this procedure. We first identified the wider class “enclosed plane figure” as the genus to which all triangles belong and then we specified “bounded by three straight lines” as the differentia that distinguishes the subclass triangles from other closed plane figures like circles, rectangles, pentagons etc. Similarly, the term ‘human being’ can be defined as ‘rational animal’ by this method.
Human beings belong to a wider class of animals, but are different from other also by virtue of their rationality. The term ‘animal’ is the genus of the term ‘human’ and rational’ is the differentia that distinguishes members of the human species from the members of other coordinates species belonging to the ‘genuses’ ‘animal’. It can be noticed that the terms ‘genus’ and species’ are relative terms.
A term can be a genus in relation to its subclasses, but a species in relation to another wider class. Thus the class of animals is a genus relative to its subclass humans, but it is a species in relation to the larger class of living things that includes plants as well.
This method of defining terms by stating their genus and differentia has certain limitations, is signifying elementary qualities like ‘red’, ‘blue’ etc. cannot be defined by this genus and differentia method, because these qualities cannot be analysed further into anything simpler. The sensed qualities like ‘red’ and ‘blue’ are identified in our experience and the difference among qualities is also learnt in experience.
Since we do not normally know how to express the once one shade of color from another, we cannot define these terms by this genus-difference method. There are unique particulars like ‘space’ and ‘time’ which cannot be brought under any class.
So, definition by genus and difference in not possible in such cases. Further, a universal class which constitutes the highest class cannot be defined by this method. A universal class which is all inclusive would be the summum genus or the highest genus.
Terms connoting universal attributes like ‘being’, ‘existent’ etc. and words standing for ultimate metaphysical categories lie ‘substance’, attribute, etc. cannot be defined by this method, since these are supposed to designate highest classes and therefore cannot be brought under any higher class.