adverb
Etymology: ME; trans. of OF en vein & ML in vanum
1. : to no end : without success or result
protests made in vain by county councils — S.P.B.Mais
2. : in an irreverent, disrespectful, or blasphemous manner
the Lord will not hold him guiltless who takes his name in vain — Deut 5:11 (Revised Standard Version)