Species (nawʿ) is a universal applicable to individuals in their complete specific nature. Genus (jins) is a broader essential constituent, and differentia (faṣl) is an essential characteristic distinguishing a kind within its genus.
Two people share the species “human.” A human and a horse share animality as a genus, without sharing the whole of their natures. In classical logic, “rational” functions as the distinguishing differentia in the standard definition of the human.
These examples clarify essential predication; they do not imply that every shared species or genus automatically makes an effective literary simile. It must be the intended aspect of a meaningful comparison.