In order to communicate the meaning of symbols, people use definitions. A definition is a process, whether verbal or otherwise, by which one individual brings another individual to know the meaning of a symbol. By the meaning of a symbol is meant its extension and/or intension. Thus, a definition tells which concept and/or which objects a symbol refers to. Note that a definition always defines a symbol; it is not meaningful to talk about the definition of a concept or an object.
About types of definitions
Methods of definitions