 Hyponymy is a hierarchical sense relationship between lexemes based on the notion of inclusion. A less general term includes the meaning of a more general term. The less general term is called the hyponym. The more general term is known as the superordinate term or hyperonym. In complex hierarchies, hyponyms can also be hyperonyms. The lexemes and fly and bee are hyponyms of the hyperonym insect and fly in term is a hyperonym of fruit fly, blue fly and brown fly. The lexemes insect and fly are hyperonyms of the concepts that are lower in the hierarchy. Hyponyms of the same superordinate term are referred to as co-hyponyms, whereas their vertical relationship with a hyperonym is one of inclusion, and for example includes insect. Their horizontal relationship with each other is one of incompatibility. Hyponymy is a transitive relation. If A is a hyponym of B and B is a hyponym of C, then A is necessarily a hyponym of C. Oddly, there are sets of elements, for example the color words, for which no superordinate term can be found. And some linguists include the relationship of synonymy within hyponymy and define it as symmetric hyponymy, where A is a hyponym of B and B one of A.