simple, a. incomplex, uncompounded, [single], [elementary], uncombined, mere; [plain], [unaffected], [artless], [naïve], [unsophisticated]; [credulous], [gullible], [silly], oafish. Antonyms: [complex], [complicated], [intricate], [artful], [crafty], elaborate.
simpleton, n. dolt, [dunce], [numskull], lackbrain, oaf, witling, [fool].
simulate, v. [pretend], [feign].
simulation, n. [pretense], [feint], [feigning], [affectation].
simultaneous, a. [contemporaneous], synchronal, synchronous.
sin, n. iniquity, [transgression], [wickedness], delinquency, peccadillo, [offense], peccancy, unrighteousness. Associated words: ponerology, hamartiology, peccable, peccability, peccant, peccavi, impeccable, impeccability.
sin, v. do [wrong], [trespass], [transgress].
sincere, a. heartfelt, [genuine], [unfeigned], undissembling. Antonyms: See insincere.
sincerity, n. [honesty], unaffectedness, [frankness]. Antonyms: [insincerity], dissimulation.
sinew, n. tendon; [muscle], thew.