half

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

• noun One of two equal parts that together constitute a whole.
• noun One part approximately equal to the remaining part.
• noun Informal A 50-cent piece.
• noun One of the two playing periods into which certain games are divided.
• noun A halfback.
• noun Chiefly British A school term; a semester.
• noun Half an hour.
• adjective Being one of two equal parts.
• adjective Being approximately a half.
• adjective Partial or incomplete.
• adverb To the extent of exactly or nearly 50 percent.
• adverb Not completely or sufficiently; partly.
• idiom (by half) By a considerable extent.
• idiom (by half) By an excessive amount.
• idiom (by halves) In a reluctant manner; unenthusiastically.
• idiom (many/much) One-and-a-half times as much or as many; 50 percent more.
• idiom (in half) Into halves.
• idiom (not half) Not at all.
• idiom (not the half of) Only a fraction or a small part of.

from The Century Dictionary.

• In an equal part or degree; by half; hence, in part; to some extent: much used in composition, and often indefinite: as, half-baked; half-dead; half-educated; half-starved.
• An erroneous form of haft.
• Being one of two equal parts; consisting of a moiety: as, a half share in an enterprise; a half ticket in a lottery.
• noun A side; a part.
• noun Part; behalf; account; sake.
• noun One of two equal parts of anything that is divisible, or that may be regarded as divisible; a moiety: usually not followed by of unless preceded by a qualifying word: as, half the miseries or pleasures of life; half a pound; half an orange; the half, one half, or the other half of an orange.
• noun Among schoolboys in England, a session; the term between vacations: a contraction of half-year. Sometimes there are three “halves” in the year.
• noun In foot-ball, a half-back. See back, n., 12.
• To divide into halves; halve; hence, loosely, to separate into parts of any relative size.

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

• noun obsolete Part; side; behalf.
• noun One of two equal parts into which anything may be divided, or considered as divided; -- sometimes followed by of.
• noun See under Better.
• noun [Colloq.] in two; an expression sometimes used improperly instead of in halves or into halves.
• noun [Obs.] in one's behalf; on one's part.
• noun to claim an equal share with another.
• noun to share equally between two.
• transitive verb To halve. [Obs.] See halve.
• adjective Consisting of a moiety, or half
• adjective Consisting of some indefinite portion resembling a half; approximately a half, whether more or less; partial; imperfect
• adjective (Zoöl.) a lemur.
• adjective (Football) See under 2d Back.
• adjective the first notch, for the sear point to enter, in the tumbler of a gunlock; the halfcock notch.
• adjective a style of bookbinding in which only the back and corners are in leather.
• adjective one who boards in part; specifically, a scholar at a boarding school who takes dinner only.
• adjective (Shipbuilding) a horizontal plan of one half a vessel, divided lengthwise, showing the lines.
• adjective (Mus.) a cadence on the dominant.
• adjective [Obs.] a slight salute with the cap.