The character 加入 is formed by combining two independent components: 加, which itself is a compound meaning "to add" (built from 力 "strength" and 口 "mouth", suggesting adding force or words), and 入, a pictograph resembling an arrowhead or wedge, meaning "to enter". Their combination creates a conceptual blend where 加 provides the notion of addition and 入 contributes the directional sense of entering into, together yielding the core idea of "to join" or "to add into".