The word 杀人犯 is formed by combining three characters sequentially to depict a specific role or identity. It begins with 杀 (shā), meaning "to kill", establishing the core action. This is followed by 人 (rén), meaning "person", which acts as the object or target of that action, creating the compound concept "to kill a person" or "homicide". Finally, 犯 (fàn), meaning "perpetrator" or "offender", is attached, designating the person who carries out that specific act. Thus, the word constructs its meaning stepwise: from action, to object of action, to the agent of that action, resulting in the complete concept of "murderer".