Smelliness is the quality of smelling strong and unpleasant — the state of being smelly, thought about as a thing on its own. Because it turns a describing word into a thing-word, it lets you talk about the amount or the degree: the smelliness of the bins, a level of smelliness, reduce the smelliness. That is its real job — you use it when you want to measure or compare, not just complain. It is a fairly rare word, and it usually sounds light or joking rather than serious. In careful or scientific writing people prefer odour: 'the odour of the sample' rather than 'the smelliness of the sample'. Almost always the meaning is negative, though a playful writer might use it for any strong smell at all, good or bad, precisely because it sounds so childish.

（發出）臭味的程度、臭度