simple

adj. (simpler, simplest) 1 understood or done easily and without difficulty. 2 not complicated or elaborate; plain. 3 not compound or complex. 4 absolute, unqualified, straightforward (the simple truth). 5 foolish; gullible, feeble-minded.  simpleness n. [latin simplus]

a. Single; not complex; not infolded or entangled; uncombined; not compounded; not blended with something else; not complicated; as, a simple substance; a simple idea; a simple sound; a simple machine; a simple problem; simple tasks.