mite

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

• noun A very small contribution or amount of money.
• noun A widow's mite.
• noun A very small object, creature, or particle.
• noun A coin of very small value, especially an obsolete British coin worth half a farthing.
• idiom (a mite) To a small degree; somewhat.
• noun Any of numerous small or minute arachnids of the order Acarina, including species that damage crops or stored food and species that are parasitic on animals and often transmit disease.

from The Century Dictionary.

• noun A small coin of any kind, of slight value; any very small sum of money. No coin seems to have been so called specifically.
• noun An English weight somewhat heavier than a grain troy.
• noun An old money of account, the twenty-fourth part of a penny.
• noun Anything very small; a very little particle or quantity: also applied to persons.
• noun A small arachnidan of the order Acarida; any acarid.
• noun Some insect like or likened to a mite, as a dust-louse (Psocus).
• noun A copper or billon coin of very small value, current in Brabant and Holland.

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

• noun (Zoöl.) A minute arachnid, of the order Acarina, of which there are many species; See acarina.
• noun A small coin formerly circulated in England, rated at about a third of a farthing. The name is also applied to a small coin used in Palestine in the time of Christ.
• noun A small weight; one twentieth of a grain.
• noun Anything very small; a minute object; a very little quantity or particle.

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

• noun A minute arachnid, of the order Acarina, of which there are many species; as, the cheese mite, sugar mite, harvest mite, etc. See Acarina.
• noun A small coin formerly circulated in England, rated at about a third of a farthing. The name is also applied to the lepton, a small coin used in Palestine in the time of Christ.
• noun A small weight; one twentieth of a grain.
• noun Anything very small; a minute object; a very little quantity or particle. Sometimes used adverbially.

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

• noun a slight but appreciable amount
• noun any of numerous very small to minute arachnids often infesting animals or plants or stored foods