The word 星际 is formed by directly combining two conceptual characters: 星 (xīng), meaning "star" or "celestial body", and 际 (jì), meaning "border", "edge", or "between". Their union creates a new, compound idea through spatial juxtaposition, where 际 defines the realm or domain of 星. It visually and conceptually paints the "border region of the stars" or the "space between stars", naturally arriving at the meaning of "interstellar" or "interplanetary". The formation is essentially a logical, almost pictorial, fusion of two core ideas into a single, coherent concept.