The word 手臂 is formed by combining two characters, each representing a distinct but connected part of the body: 手 (shǒu), which pictographically represents a "hand", and 臂 (bì), which conceptually means "arm". Together, they create a compound that visually and semantically extends from the appendage at the end (the hand) back along the entire limb it is attached to (the arm), effectively forming a single concept for the whole upper limb from shoulder to fingers. This mirrors how the physical arm and hand are structurally one continuous unit, with the character for the more specific, active part (手) placed first to modify and connect to the broader, supporting part (臂).