TheUltimateWinnerDepending on the context, “human” can appear as a noun or an adjective.
“To err is human.”
In this case, “human” is a subject complement following the ‘-to be’ verb.
Basically, it’s a fancy grammar term to describe what could be a noun (predicate nominative) or an adjective (predicate adjective).
Depending on how deep a rabbit hole you want to jump down:
https://en.m.wikipedia.org/wiki/Subject_complementthe sentence, “To err is human”, is a quote from a poem by Alexander Pope.
Written without the rhetorical effect:
“It is human to err.”
Like other nouns, “human” can function as a noun-adjective modifying another noun:
ex 1: “Only a handful of human minds can understand this work.”
What kind of “minds” can understand this work? HUMAN minds
So “human” is modifying the noun “minds as an adjective.
ex 2: “Humans are the only living beings to make use of fire.”
In this example “humans” functions as a noun in the subject slot.
Luckily, we don’t have to delve to deeply into extensive Grammar and Linguistics to understand the sentences on the GMAT.
I hope something was helpful. All the best.
Posted from my mobile device