Ma'anar ƙamus na "yanayin muhalli" yana nufin yanayi, inganci, ko yanayi na duniyar halitta ko kewaye wanda zai iya tasiri ga rayayyun halittu ko yanayin muhalli. Ya ƙunshi abubuwa daban-daban kamar ingancin iska, ingancin ruwa, zafin jiki, zafi, hazo, ingancin ƙasa, flora da fauna, gurɓatawa, da sauran abubuwan jiki, sinadarai, da ilimin halitta waɗanda ke shafar yanayin yanayi. Yanayin muhalli na iya samun tasiri kai tsaye ko kai tsaye kan lafiyar ɗan adam, namun daji, tsiro da tsiro, da daidaiton muhalli. Nazari da fahimtar yanayin muhalli yana da mahimmanci don magance matsalolin muhalli, haɓaka ayyuka masu ɗorewa, da kuma yanke shawarar da suka shafi kula da muhalli da kiyayewa.