messenger: P. and V. ἄγγελος, ὁ or ἡ. V. πομπός, ὁ; see also ambassador.
go-between: P. διάγγελος, ὁ.
spy: P. and V. κατάσκοπος, ὁ, σκοπός, ὁ (Thuc. but rare P.), V. ὀπτήρ, ὁ, κατοπτήρ, ὁ, κατόπτης, ὁ.
