STRONG—robust, sturdy, powerful. (Weak.)
STUPID—dull, foolish, obtuse, witless. (Clever.)
SUBJECT—exposed to, liable, obnoxious. (Exempt.)
SUBJECT—inferior, subordinate. (Superior to, above.)
SUBSEQUENT—succeeding, following. (Previous.)
SUBSTANTIAL—solid, durable. (Unsubstantial.)
SUIT—accord, agree. (Disagree.)
SUPERFICIAL—flimsy, shallow, untrustworthy. (Thorough.)
SUPERFLUOUS—unnecessary. (Necessary.)
SURROUND—encircle, encompass, environ.