the word trilogy is a direct borrowing from the greek trilogia, which itself is a compound of tri-, meaning "three", and -logia, denoting "a speaking or discourse". in ancient greek drama, a trilogy referred to a set of three tragedies performed together as a connected narrative. the term entered scholarly english in the late 18th century, retaining the core concept of a set of three. over time, its application broadened from its specific theatrical origin to encompass any group of three related literary or artistic works, such as novels or films, that together form a cohesive whole.

Structure: tri (three) + logy (discourse, study) - tri: from greek and latin; a combining form meaning "three". - logy: from greek -logia, via latin -logia; a combining form meaning "a speaking, discourse, treatise, doctrine, theory, science".