The word 障碍 is formed by combining two characters with closely related meanings to create a single, reinforced concept. The first character, 障, originally depicted a hill or mound (from its radical 阜, meaning "hill") and carries the core meaning of "to block" or "a barrier". The second character, 碍, incorporates the "stone" radical (石) and means "to hinder" or "obstruct". When placed together, their individual notions of creating a physical blockade and causing hindrance merge to form the comprehensive idea of an "obstacle" or "impediment", where the whole meaning is greater than the sum of its parts.