smell: implies solely the sensation without suggestion of quality or character or source: an odd ~ permeated the room.
scent: applies to the characteristic smell given off by a substance, an animal, or a plant and stresses the source of the sensation: dogs trained to detect the ~ of narcotics.
odor: may imply a stronger or more readily distinguished scent or it may be equivalent to smell: a type of cheese with a very pronounced ~.
aroma: suggests a somewhat penetrating, pervasive, or sometimes pungent, but usually pleasant odor: the ~ of freshly ground coffee. 对这个词的解释用了4个以p开头的形容词，因此比较好记
smell仅表示嗅觉,不涉及特性、来源；scent特有气味，强调来源；odor强烈易于分辨的scent，或和smell一样泛指气味；aroma刺鼻弥漫，但一般好闻气味
记忆方法： 1）首字母SSOA重组为AS SO作为如此<==气味 4个词全都用前一个词解释后一个词，因此比较好记
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4）气味的意思是使能被嗅觉感知的属性mean the quality that makes a thing perceptible to the olfactory sense. 相应的the gustatory sense是味觉
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