less

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Not as great in amount or quantity.
• adjective Lower in importance, esteem, or rank.
• adjective Consisting of a smaller number.
• preposition With the deduction of; minus.
• adverb To a smaller extent, degree, or frequency.
• noun A smaller amount.
• noun Something not as important as something else.
• idiom (less than) Not at all.
• idiom (much/still) Certainly not.

from The Century Dictionary.

• Unless.
• A common English suffix forming, from nouns, adjectives meaning ‘without’ (lacking, wanting, void of, destitute of) the thing or quality denoted by the noun: as. childless, without a child; fatherless, without a father; endless, without end; hopeless, without hope; leafless, without leaves; shameless, without shame; so motherless, penniless, faithless, godless, graceless, lawless, witless, remediless, tasteless, etc.
• To make less; lessen.
• To become less; lessen.
• In a smaller or lower degree; to an inferior extent, amount, etc.; in a decreased or abated way or manner: as, less prudent; less carefully executed; to exaggerate less; to think less of a person.
• Not so much or so large; of smaller quantity, amount, bulk, or capacity; inferior in dimensions, extent, or duration: as, less honor or reward; less profit or possessions; less time; less distance; less scope or range; the reward is less than he deserves; a man of less courage or ability; an article of less, weight or value.
• Not so great, considerable, or important; of smaller scope or consequence; lower in the scale: as, St. James the Less; his honors are less than his deserts.
• Synonyms Smaller, Less, Fewer. Smaller is rather more exact than less, but is used freely of persons and of things both concrete and abstract: as, a smaller man, soul, size. Less is not used of persons: as, less trouble, happiness, size, degree; less of an evil. With reference to size and number, the proper words are smaller and fewer. “This apple is less than that,” “There were less people there than I expected,” are inelegant and erroneous, although similar expressions are often used both in speech and in writing. While the latter, however, is in excusable, the former may be used sparingly without offense in certain collocations, especially in poetry. The allusion to the mustard-seed in Mark iv. 31 appears to be the only example in the Bible of the use of less in the sense of ‘smaller in size.’ In Shakspere's plays the word occurs more than two hundred times, and in Milton's poems more than a hundred; in the former it is used only four or five times and in the latter three times in the sense of ‘smaller in size,’ and never in that of ‘fewer.’

from the GNU version of the Collaborative International Dictionary of English.

• noun A smaller portion or quantity.
• noun The inferior, younger, or smaller.
• adjective Smaller; not so large or great; not so much; shorter; inferior
• conjunction obsolete Unless.
• adverb Not so much; in a smaller or lower degree
• transitive verb obsolete To make less; to lessen.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adverb To smaller extent
• adverb In lower degree
• preposition Minus; not including
• verb obsolete To make less; to lessen.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective (nonstandard in some uses but often idiomatic with measure phrases) fewer
• adverb comparative of little
• adjective (comparative of `little' usually used with mass nouns) a quantifier meaning not as great in amount or degree
• adverb used to form the comparative of some adjectives and adverbs
• adjective (usually preceded by `no') lower in quality