The word "胚芽" is formed by combining two characters: "胚" meaning embryo, composed of the radical "月" (indicating organic tissue) and the phonetic component "丕" for pronunciation, and "芽" meaning sprout, composed of the radical "艹" (indicating plant) and the phonetic component "牙" for pronunciation. Together, they create a compound word where "胚" conveys the embryonic aspect and "芽" conveys the plant-based sprouting, resulting in the meaning "plant embryo" or "germ".