μάτην G3155
mátēn · mat'-ane · Adverb
accusative case of a derivative of the base of μασσάομαι (through the idea of tentative manipulation, i.e. unsuccessful search, or else of punishment); folly, i.e. (adverbially) to no purpose:--in vain.
2 Occurrences in the King James Bible
Matthew 15:9But in vain they do worship me, teaching for doctrines the commandments of men.
Mark 7:7Howbeit in vain do they worship me, teaching for doctrines the commandments of men.