I have been wondering how something smells.
How come something smells the same as other thing? What is similar in them?
Like what is the chemistry behind a particular smell of a substance?

For example compounds with SH (thiol) smell awful and similar, so what is similar between them? I know SH, but I am asking why can't they smell different.

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    $\begingroup$ You aren't surprised that two things may have the same color, are you? $\endgroup$ – Ivan Neretin Aug 7 '17 at 11:56
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    $\begingroup$ I'm afraid unless you provide a certain example you question is way too broad. $\endgroup$ – andselisk Aug 7 '17 at 11:57
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    $\begingroup$ This is probably more of a biology question, no? Smell is a property of the interaction between a molecule and the receptors in the nose. Although compounds with a similar smell may have the same functional groups, they may be very different. On the other hand, there is D/L- limonene that has a different smell for each of the two isomers. $\endgroup$ – gilleain Aug 7 '17 at 12:38
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    $\begingroup$ The bit in your post that's suggestive of being off-topic(ish): "smell awful and similar". Smell is human perception, not a physical quantity, and hence doesn't really pertain to "pure" Chemistry. Sure, in Chemistry we talk about "smell" a lot, but that's really just limited to the laboratory ( "Phenolic" smell, "Pungent" smell, etc), but wanting to know how something has a particular odor is really more of a human physiology question. I'm not saying there's no Chem. involved...but this is way better off on the Biology.SE. As such, I vote to keep this closed. $\endgroup$ – paracetamol Aug 7 '17 at 15:55
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    $\begingroup$ Question could be migrated, but premise isn't true, I'm pretty sure one can make thiols with distinct smell. It's not that simple. $\endgroup$ – Mithoron Aug 7 '17 at 18:14