What do you mean by Mereology?

Mereology is the branch of philosophy that studies the relationships between parts and wholes. It examines how parts combine to form wholes, the principles governing these relationships, and the concepts of part, whole, and part-whole relations. Mereology contrasts with set theory, as it deals with parts and wholes rather than sets and members. It is concerned with questions such as whether parts are dependent on wholes, how parts interact within a whole, and the nature of composition and decomposition.