The formation of 未知 (wèizhī, "unknown") is a conceptual fusion where the first character 未 ("not yet" or "negation") directly modifies and limits the scope of the second character 知 ("to know" or "knowledge"). This creates a single, indivisible idea where the sense of negation is applied to the state of knowing, producing a new, unified concept meaning "that which is not known" or "the unknown". It functions as a fixed idea-unit, where the combined meaning is greater than a simple sum of its parts.