Few / Less
Few / LessBoth these words are adjectives, but "few" is usually used to describe countable nouns while "less" is used to describe noncountable nouns. Countable nouns are often physical whereas noncountable ones are often abstract or nonphysical:
If you memorize the phrase "few units = less quantity," you will remember the distinction—"few" is for countables occurring in units, while "less" is for noncountables occurring in quantity.
As often happens in English, exceptions do arise. Sentences involving periods of time, sums of money, or specific measurements usually require "less":