Alcohol

Alcohol, term applied to members of a group of chemical compounds that contain the OH group. Also commonly used to refer to the specific compound ethyl alcohol, or ethanol. The word is derived from the Arabic al-kuhl, or kohl, a fine powder of antimony used as an eye makeup. The word alcohol originally denoted any fine powder, but the alchemists of medieval Europe later applied it to essences obtained by distillation, and this led to the current usage.

Alcohol molecules can possess one, two, or three hydroxyl (OH-) groups. Molecules containing one hydroxyl group are monohydric ("mono-" meaning "one"), those with two hydroxyl groups are dihydric ("di-" indicating "two"), and those with three are trihydric ("tri-" meaning "three"). The number of hydroxyl groups affects the properties of the compound. Methanol is a light, volatile liquid while ethylene glycol (recommended name ethane-1,2-diol) is viscous, and glycerol (or glycerine, or the recommended scientific name propane-1,2,3-triol) is the most viscous of the three.