[tril.o.gy] n, pl -gies [Gk trilogia, fr. tri- + -logia -logy] (ca. 1661): a series of three dramas or literary works or sometimes three musical compositions that are closely related and develop a single theme
TRILOGY
Meaning of TRILOGY in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012