simple in WordNet English dictionary

1. apart from anything else; without additions or modifications
   "only the bare facts"; "shocked by the mere idea"; "the simple passage of time was enough"; "the simple truth"
   bare  mere  simple 
   
2. exhibiting childlike simplicity and credulity
   "childlike trust"; "dewy-eyed innocence"; "listened in round-eyed wonder"
   childlike  wide-eyed  round-eyed  dewy-eyed  simple 
   
3. lacking mental capacity and subtlety
   dim-witted  simple  simple-minded 
   
4. easy and not involved or complicated
   "an elementary problem in statistics"; "elementary, my dear Watson"; "a simple game"; "found an uncomplicated solution to the problem"
   elementary  simple  uncomplicated  unproblematic 
   
5. (botany) of leaf shapes; of leaves having no divisions or subdivisions
   simple  unsubdivided 
   
6. having few parts; not complex or complicated or involved
   "a simple problem"; "simple mechanisms"; "a simple design"; "a simple substance"
   simple 
   
7. unornamented
   "a simple country schoolhouse"; "her black dress--simple to austerity"
   simple 
   

1. a person lacking intelligence or common sense
   simpleton  simple 
   
2. any herbaceous plant having medicinal properties
   simple