noun

• (biology, taxonomy) A category in the classification of organisms, ranking below family (Lat. familia) and above species.
• A taxon at this rank.
• A group with common attributes.
• (topology, graph theory, algebraic geometry) A natural number representing any of several related measures of the complexity of a given manifold or graph.
• (semantics) Within a definition, a broader category of the defined concept.
• (music) A type of tuning or intonation, used within an Ancient Greek tetrachord.