forming words, with the meanings:
opposing or hostile to
anti-abortion
preventing
anti-roll bar
being a rival
antipope
combating or defending against
anti-aircraft
antitank
opposite in kind to
anticlimax
anti-hero
of the same kind but situated opposite or in the opposite direction to
antipodes
anticlockwise
being the antimatter counterpart of
antineutrino
[Middle English via Old French and Latin from Greek anti-]