The word 绳子 is formed by combining the character 绳, which originally depicted a pictograph of a coiled rope or cord, with the character 子, which here functions not as a standalone word but as a common suffix added to nouns. This suffix 子 often conveys a sense of a concrete, tangible object or a familiar, everyday item, softening the root word and transforming the abstract concept of "rope" (绳) into the more common, physical object we handle: "a piece of string" or "a rope". Therefore, the formation is essentially a root meaning (绳) plus a nominalizing and concretizing suffix (子) to create a standard word for the everyday object.