A human; is the existence that has the capacity to express and manifest all of the divine names. 

The entire existence, including animals, are compositions, yet the potential to be the vicegerent of Allah is specific to humans.

A human is what we call man in respect to his compositional make-up. 

“I too am a human like you!” (Hadith)

This means: “My existence, like yours, is nothing other than a composition of divine names."