1. [adj]  (logic) of a proposition; having a truth value determined by observation or facts, as"all men are arrogant"
2. [adj]  involving or of the nature of synthesis (combining separate elements to form a coherent whole) as opposed to analysis; "limnology is essentially a synthetic science composed of elements...that extend well beyond the limits of biology"- P.S.Welch

SYNTHETICAL is a 11 letter word that starts with S.