alcohol vs diol

alcohol and diol both are nouns.

Word	Noun	Adjective	Verb	Adverb
alcohol	Yes	No	No	No
diol	Yes	No	No	No

As nouns, diol is a hyponym of alcohol; that is, diol is a word with a more specific, narrower meaning than alcohol:

alcohol: any of a series of volatile hydroxyl compounds that are made from hydrocarbons by distillation
diol: any of a class of alcohols having 2 hydroxyl groups in each molecule

alcohol (noun)	diol (noun)
a liquor or brew containing alcohol as the active agent	any of a class of alcohols having 2 hydroxyl groups in each molecule
any of a series of volatile hydroxyl compounds that are made from hydrocarbons by distillation