simple

absolute arcadian austere bare barest benighted blockheaded careless chaste childlike classic clean clean cleanest cleanest clearest clear clearer commonest common credulous crude crudest daft daftest denser dense dimwitted doltish dopey doting downright down to earth dry dull dupable duller earthy easy as pie easiest easy easier effortless elegant facile familiar fatuous featherbrained feeble-minded foolish forthright guileless gullible harmless homelike homely homey homespun humble humble humblest humblest ignoble imbecile imbecilic ingenuous innocent literal loopy low lowly main mere mindless modest modest more elegant more familiar more readable more understandable more modest more modest more natural more primary more primary more virginal most primary most primary most virginal naive naked natural nominal nothing to it nothing to it oafish open-and-shut open and shut/open-and-shut ordinary oversimplified pastoral pellucid perfect plain plain primary/prime primitive primary primest purest pure readable rudimentary rude rural rustic rustic self-effacing senseless shallow shallower sheer silly simple-minded single slow slowest slower soft soft softer softer softheaded spartan spontaneous stark stupid thick-witted tomfool unaffected unassuming uncomplicated understandable undiluted unintelligent unimposing unoffensive unqualified unprocessed unostentatious unmitigated unpretentious unsuspecting unvarnished unwashed user-friendly unworldly very voluminous virginal