Full Idea
Traditional definitions are generalized identities (so definiendum and definiens can replace each other), in which the sentential is primary (for use in argument), and they involve reduction (and hence eliminability in a ground language).
Gist of Idea
Traditional definitions are general identities, which are sentential and reductive
Source
Anil Gupta (Definitions [2008], 2.2)
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.9