less vs fewer

less and fewer both are adjectives.

Word	Noun	Adjective	Verb	Adverb
less	No	Yes	No	Yes
fewer	No	Yes	No	No

less (adjective)	fewer (adjective)
(comparative of `little' usually used with mass nouns) a quantifier meaning not as great in amount or degree	(comparative of `few' used with count nouns) quantifier meaning a smaller number of
(nonstandard in some uses but often idiomatic with measure phrases) fewer
(usually preceded by `no') lower in quality

less (adverb)	fewer (adverb)
used to form the comparative of some adjectives and adverbs, indicates that the adjective or adverb is less of something
comparative of little