Trilogy
Pronunciation : Tril"o*gy
Part of Speech : n.
Etymology : [Gr. Tri-) + trilogie.]
Definition : Defn: A series of three dramas which, although each of them is in one sense complete, have a close mutual relation, and form one historical and poetical picture. Shakespeare's " Henry VI." is an example. On the Greek stage, a drama, or acted story, consisted in reality of three dramas, called together a trilogy, and performed consecutively in the course of one day. Coleridge.
Source : Webster's Unabridged Dictionary, 1913