serious in intention, purpose, or effort; sincerely zealous

an earnest worker.

showing depth and sincerity of feeling

earnest words; an earnest entreaty.

seriously important; demanding or receiving serious attention.

full seriousness, as of intention or purpose

to speak in earnest.

adjective

flippant , unconcerned , unenthusiastic , unpassionate , unpurposeful , unthoughtful , insincere , thoughtless , trivial , unimportant , unserious

adjective

ardent , busy , devoted , diligent , eager , fervent , fervid , heartfelt , impassioned , industrious , keen , passionate , perseverant , purposeful , sedulous , sincere , urgent , vehement , warm , wholehearted , zealous , close , constant , determined , firm , fixed , for real , grave , intent , mean business , meaningful , no-fooling , no-nonsense , playing hard ball , resolute , resolved , sedate , sober , solemn , somber , stable , staid , steady , thoughtful , weighty , businesslike , sobersided , serious , heavy , momentous , severe , affectionate , engage , honest , intense , token , unfeigned

noun

guaranty , pledge , security , token , warrant