The compound adjective "theory-based" is a modern English formation that transparently combines two established elements. The first element, "theory," originates from the Greek 'theōria', meaning a looking at, viewing, or contemplation, which evolved in English to signify a system of ideas intended to explain something. The second element, "based," derives from the past participle of the verb 'base', which entered English via French from the Latin 'basis', meaning a foundation or pedestal. The logic of the word is entirely compositional: it literally denotes something that is "founded upon a theory," directly linking the abstract explanatory system (theory) to the concept of providing a foundational support (based) for a practice, model, or approach.

Structure: theory (abstract system) + based (founded on) - theory: From Greek 'theōria' (contemplation, speculation). Functions as the core noun, specifying the source or foundation. - based: From Old French 'baser' (to lower, found), ultimately from Latin 'basis' (foundation). Functions as a participial adjective suffix meaning "having as a foundation".