As nouns, they can be the same way: "The smell / odor from the trash can made me sick to my stomach." Odor is usually something negative, but it doesn't have to be. "You have to do something about that odor coming from your tennis shoes." Smell can be something neutral or mildly pleasant. "In the forest, the air was filled with the smell of wet leaves." Smell can also be a verb: "I smelled something burning." "The fish smelled old." Other "smelling" words: If it's a "pretty" or sweet smell, you can use "fragrance", which is positive. "The fragrance of her perfume reminded me of the roses in my grandmother's garden." "Aroma" is also a positive smell. "The aroma of freshly baked bread filled the house." "Stench" is a disgusting odor: "You couldn't avoid the stench of the dead animal in the middle of the road."

Hi Najeeb. The word 'odor' is always a noun, 'smell' can be a noun or a verb. as a noun, they mean the same thing and both can refer to either a pleasant or an unpleasant scent. Example; Can you smell the odor of cooking in the kitchen? Yes it's the lovely smell of lamb shaslicks being cooked by my mother. Example; Oh, what is that terrible odor in this village? I think that it's the smell of horse manure.