The word 胸部 is formed by combining two characters: 胸, which means "chest" or "thorax", referring specifically to the area of the body between the neck and abdomen; and 部, which means "part", "section", or "region". When joined, they create a compound that literally signifies the "chest region" or "chest part", directly constructing its meaning from the sum of its components, one specifying the body area and the other categorizing it as a distinct zone or division of the body.