Mercaptans are the sulfur alcohols. Essentially, this means they are hydrosulfides, like an alcohol radical, only containing sulfur in place of oxygen.

They are colorless liquids having an odor resembling that of garlic; strong and repulsive. Looking at its binding states for metals, particularly mercury, one can see the reason for its name, from the Latin mercurius captans, laying hold of mercury.

Examples:

Methyl mercaptan - CH3SH
Ethyl mercapatan - C2H5SH