Source : Webster's Revised Unabridged Dictionary (1913)

Archi- \Ar"chi-\ [L., archi-, Gr. 'archi-, a prefix which is
   from the same root as 'a`rchein to be first, to begin; 'archh
   the first place, beginning; 'archo`s chief. Cf. AS. arce-,
   erce-, OHG. erzi-, G. erz-.]
   A prefix signifying chief, arch; as, architect,
   archiepiscopal. In Biol. and Anat. it usually means
   primitive, original, ancestral; as, archipterygium, the
   primitive fin or wing.