The word 跑步 is formed by combining two individual characters, each contributing a key aspect of the action. The first character, 跑 (pǎo), itself means "to run" and is composed of the foot radical (足) paired with 包 (bāo), suggesting a wrapped or propelled motion. The second character, 步 (bù), means "step" and is a pictographic representation of two feet (止) walking in sequence. Therefore, 跑步 is a logical compound where 步 defines the fundamental unit of movement (steps) and 跑 intensifies it to the specific, faster action of running, creating a complete visual and conceptual picture of the activity.