肥料 (féi liào) is the general term for any fertilizer, including both chemical and organic types. 化肥 (huà féi) specifically refers to chemical fertilizer, while 粪 (fèn) means manure or dung (animal waste). 肥 (féi) as a noun is less common on its own and usually appears in compounds like 化肥 or 肥料 itself.