Chemists actually find it simpler to define a general odor of rotten eggs as a baseline, and the LACK of rotten eggs as a distinct smell.

"Chemist Eggs", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License

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Chemists actually find it simpler to define a general odor of rotten eggs as a baseline, and the LACK of rotten eggs as a distinct smell.