In anatomy:

Facet is a feature of the Eclipse (software) Software Development Platform

Facet, a flat surface of a geometric shape, e.g., of a gemstone.

Facet in mathematics (topology, geometry) is a special type of face.

A facet is part of a compound eye.

A facet joint is a vertebral joint.

Facet in information retrieval is one of several attributes that items have and can be used for navigation.

FACET is the Faculty Colloquium on Excellence in Teaching at Indiana University.