Cohyponym

My art exchange from Eliandme was a super piece of writing which (purposely) included some words that were new to me. Amongst these was cohyponym.

A cohyponym is a word or phrase that shares the same hypernym as another word or phrase.

A hypernym is a word whose meaning denotes a superordinate or superclass. So, for example, animal is a hypernym of dog.

Cat is therefore a cohyponym of dog.