Some food for thought (inspired by D. Perdue's "Debate inTibetan buddhism", Chapter 3, i.e. partially quoted and arbitrarily amended):
A definition may be considered to be the actual object (phenomenon) defined and necessarily refers to the definiendum which may be considered to be the name designated to that object (or designated to the phenomenon which is transformed into an object of thought by this designation). Of course since a conventional "name" in most cases evokes an idea and since the combination of "name" and idea is often referrred to as "concept" actually the definition is a verbal expression intended to standardize the idea aspect of a concept by means of a verbal delineation of what it is suggested to mean inter-individually thus trying to exclude everything else and thus suggesting a convention.
A particul definition, or characterizer, and its definiendum, or that characterized, are mutually inclusive. Mutual inclusion has two components. First the things mutually inclusive must be phenomena which are different that is they must be not exactly the same in both name and meaning. Obviously, any two mutually inclusive phenomena must be different in name, but their meaning, all the phenomena which they include or all those things to which their names can properly refer, must be just the same. The second requirement of mutually inclusive phenomena is that they be mutually pervasive; whatever is the one is necessarily the other. Both of these requirements of mutually inclusive phenomena obtain for any particular definition and its definiendum.The definition is considered to be the actual object defined and the definiendum is considered to be the name designated to that object.