النوع وهو كلي مقول على كثيرين متفقين بالحقائق في جواب «ما هو؟»
A species is a universal predicated of many things agreeing in their specific essences, in response to “What is it?”
The genus definition says differing in essences, while the species definition says agreeing in essences. This is the critical contrast.
Zayd, Amr and Khalid differ as persons but share the human essence. Human answers what each is; hence it functions as species.