The word "一部分" is formed through a logical, sequential combination of its three constituent characters: "一" (one), "部" (section/part), and "分" (division/portion). It constructs the concept by starting with the numeral "one", attaching it to the general idea of a "section", and then further specifying that section as a "division" or share of a larger whole. This creates a composite meaning where the sense of a single, discrete segment is built up additively, with each character refining and concretizing the notion initiated by the previous one.