simple

absolute arcadian austere bare barest benighted blockheaded careless chaste childlike classic clean clean cleanest cleanest clear clearest clearer common commonest credulous crudest crude daft daftest denser dense dimwitted doltish doting dopey downright down to earth dry dupable dull duller easy as pie earthy easy easier easiest 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 readable more familiar 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 primitive primary/prime primary primest pure purest readable rude rudimentary rural rustic rustic self-effacing senseless shallow shallower sheer silly single simple-minded slowest slower slow softer softer soft soft 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 virginal very voluminous