vain 
/ˈveɪn/ adjective
vain·er; vain·est /ˈveɪn/ adjective 1 [also more vain; most vain] : too proud of your own appearance, abilities, achievements, etc. : conceited
▪ She is very vain about her appearance. ▪ He is the vainest man I know. 2 : having no success : not producing a desired result
▪ They made a vain [=unsuccessful] attempt to escape. ▪ A vain effort to quell the public's fears only made matters worse. ▪ Volunteers searched the area in the vain hope of finding clues.
▪ She is very vain about her appearance. ▪ He is the vainest man I know.
▪ They made a vain [=unsuccessful] attempt to escape. ▪ A vain effort to quell the public's fears only made matters worse. ▪ Volunteers searched the area in the vain hope of finding clues.
in vain
: without success : without producing a good or desired result
▪ We searched in vain for the missing earring. [=we searched for the missing earring but did not find it] ▪ He tried in vain to get the baby to sleep. ▪ Her suffering will not be in vain. [=something good will happen because of her suffering]
▪ We searched in vain for the missing earring. [=we searched for the missing earring but did not find it] ▪ He tried in vain to get the baby to sleep. ▪ Her suffering will not be in vain. [=something good will happen because of her suffering]
take someone's name in vain
: to use (a name, especially the name of God) in a way that does not show proper respect
▪ He took God's name in vain. ▪ (humorous) I thought I heard someone taking my name in vain. [=saying my name]
▪ He took God's name in vain. ▪ (humorous) I thought I heard someone taking my name in vain. [=saying my name]
— vain·ly adverb
▪ We tried vainly to get a taxi. ▪ Volunteers vainly searched for clues.
▪ We tried vainly to get a taxi. ▪ Volunteers vainly searched for clues.
