The word 杯子 is formed by combining the meaningful character 杯, which means "cup" or "vessel for drinking", with the character 子, which here functions not for its literal meaning but as a common nominal suffix. This suffix 子 is attached to the root 杯 to create a concrete, stand-alone noun for an everyday object, following a standard pattern in Mandarin where 子 is added to turn a concept or a bound root into a free, common noun.