The word "镇子" is formed by combining the core character "镇", which means "town" or "garrison", with the very common suffix "子". This suffix adds no independent meaning but attaches to the root to create a more colloquial, familiar, and often slightly diminutive concrete noun. The process essentially takes the abstract concept of a "town" and transforms it into a word that feels more like a specific, tangible place one might live in or refer to in everyday speech.