arch- /ɑːtʃ, ɑːk $ ɑːrtʃ, ɑːrk/ BrE AmE prefix
[ Language: Old French ; Origin: Latin arch- , archi- , from Greek , from archein 'to begin, rule' ]
belonging to the highest class or rank:
an archbishop (=an important ↑ bishop )
our archenemy (=our worst enemy)
the company’s arch-rivals (=main competitors)