Noun

• S: (n) simple (any herbaceous plant having medicinal properties)
• S: (n) simpleton, simple (a person lacking intelligence or common sense)

Adjective

• S: (adj) simple (having few parts; not complex or complicated or involved) "a simple problem"; "simple mechanisms"; "a simple design"; "a simple substance"
• S: (adj) elementary, simple, uncomplicated, unproblematic (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"
• S: (adj) bare, mere, simple (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"
• S: (adj) childlike, wide-eyed, round-eyed, dewy-eyed, simple (exhibiting childlike simplicity and credulity) "childlike trust"; "dewy-eyed innocence"; "listened in round-eyed wonder"
• S: (adj) dim-witted, simple, simple-minded (lacking mental capacity and subtlety)
• S: (adj) simple, unsubdivided ((botany) of leaf shapes; of leaves having no divisions or subdivisions)
• S: (adj) simple (unornamented) "a simple country schoolhouse"; "her black dress--simple to austerity"