'Human' is a being distinguished from other creatures by certain characteristics and features opposed to animals, machines etc.It is a race belonging to mankind.
human error, human nature ,human resources, human being....
'human' could also mean kind or considerate.
'human' is both a noun and an adjective, while 'humanity' is only a noun.
It refers to the human race as a whole or the facts and quality of being human.
It could also mean kindness and mercy.
'the humanities' as a term has an other specific meaning ,referring to the study of literature,philosophy and the arts.
It could also refer specifically to the languages and literatures of ancient Greece and Rome; they call it also 'the classics'.