Simple, foolish, silly, fatuous, asinine can all mean actually or apparently deficient in intelligence.
Silent vs Uncommunicative vs Taciturn vs Reticent vs Reserved vs Secretive vs Close vs Close-lipped vs Closemouthed vs Tight-lipped
Silent, uncommunicative, taciturn, reticent, reserved, secretive, close, close-lipped, closemouthed, tight-lipped are comparable when they mean showing restraint in speaking to or with others.
Sign vs Signal
Sign, signal can both mean a motion, an action, a gesture, or a word by which a command or wish is expressed or a thought is made known.
Sign vs Mark vs Token vs Badge vs Note vs Symptom
Sign, mark, token, badge, note, symptom can denote a sensible and usually visible indication by means of which something not outwardly apparent or obvious is made known or revealed.
Sigh vs Sob vs Moan vs Groan
Sigh, sob, moan, groan are comparable as verbs when they mean to emit a sound, commonly an inarticulate sound, indicative of mental or physical pain or distress and as nouns, such a sound.
Shy vs Bashful vs Diffident vs Modest vs Coy
Shy, bashful, diffident, modest, coy can mean showing disinclination to obtrude oneself in the presence or company of others.
Shrewd vs Sagacious vs Perspicacious vs Astute
Shrewd, sagacious, perspicacious, astute can all mean acute in perception and sound in judgment, especially in reference to practical affairs.
Showy vs Pretentious vs Ostentatious
Showy, pretentious, ostentatious can mean making or presenting an outward display that is by implication greater than what is necessary or justifiable.
Show vs Exhibit vs Display vs Expose vs Parade vs Flaunt
Show, exhibit, display, expose, parade, flaunt can all mean to present in such a way as to invite notice or attention.
Show vs Manifest vs Evidence vs Evince vs Demonstrate
Show, manifest, evidence, evince, demonstrate are comparable when they mean to reveal something outwardly by or as if by a sign or to serve to make something outwardly apparent or visible.
Shout vs Yell vs Shriek vs Scream vs Screech vs Squeal vs Holler vs Whoop
Shout, yell, shriek, scream, screech, squeal, holler, whoop are comparable when they mean as verbs to make or utter a loud and penetrating sound that tends or is intended to attract attention and, as nouns, a sound or utterance of this character.
Shorten vs Curtail vs Abbreviate vs Abridge vs Retrench
Shorten, curtail, abbreviate, abridge, retrench can all mean to reduce in extent, especially by cutting.