The word 要是 is formed through the conceptual blending of its two component characters: 要, which carries the core ideas of "wanting", "requiring", or "essential matter", and 是, the fundamental verb "to be". Their combination creates a new, unified meaning not by simple addition, but by 是 acting to substantiate and concretize the hypothetical or necessary condition implied by 要. It essentially frames a thought as "the required scenario is"... or "the essential point is that"..., thereby evolving from literal components into a single lexical unit that introduces a supposition or condition.