interval

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

• noun A space between objects, points, or units, especially when making uniform amounts of separation.
• noun An amount of time between events, especially of uniform duration separating events in a series.
• noun A segment of an athletic workout in which an athlete runs, swims, or does other exercise over a series of predetermined distances at regular time increments with intermittent rests.
• noun A set of numbers consisting of all the numbers between a pair of given numbers along with either, both, or none of the endpoints.
• noun A closed interval.
• noun An open interval.
• noun A half-open interval.
• noun A line segment representing the set of numbers in an interval.
• noun Chiefly British An intermission, as between acts of a play.
• noun Music The difference, usually expressed in the number of steps, between two pitches.
• idiom (at intervals) In a series separated by space or time.

from The Century Dictionary.

• noun A vacant or unobstructed space between points or objects; an intervening vacancy; an open reach or stretch between limits: as, the intervals between the ranks of an army.
• noun Specifically, a low level tract of land, as along a river, between hills, etc. Also intervale.
• noun Any dividing tract in space, time, or degree; an intervening space, period, or state; a separating reach or stretch of any kind: with reference either to the space itself or to the points of separation or division: as, an interval of rocky ground between meadows; to fill up an interval in. conversation with music; an interval of ease or of relapse in disease; a lucid interval in delirium; to set trees at intervals of fifty feet; to breathe only at long intervals; the clock strikes at intervals of an hour.
• noun Specifically, in entomology, one of the spaces between longitudinal striæ of the elytra. When the striæ are regular, both they and the intervals are numbered from the suture outward.
• noun In music, the difference or distance in pitch between two tones.
• noun The values given in the first column are those of the ideal intervals, such as are secured by using pure intonation; those given in the second column are those of equally tempered intonation, such as is used on keyed instruments, like the pianoforte and the organ. (See intonation and temperament.) A diatonic, interval is one that occurs between two tones of a normal major or minor scale. A chromatic interval is one that occurs between a tone of such a scale and a tone foreign to that scale. An enharmonic interval is one on an instrument of fixed intonation, that is apparent only in the notation, being in fact a unison, as, on the pianoforte, the interval from F♮ to G♭. In musical science the theory of intervals is introductory to that of chords and to harmony in general.
• noun In logic, a proposition.
• noun During or between intervals; between whiles or by turns; occasionally or alternately: as, to rest at intervals.

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

• noun Local, U. S. A tract of low ground between hills, or along the banks of a stream, usually alluvial land, enriched by the overflowings of the river, or by fertilizing deposits of earth from the adjacent hills. Cf. bottom, n., 7.
• noun A space between things; a void space intervening between any two objects.
• noun Space of time between any two points or events
• noun A brief space of time between the recurrence of similar conditions or states
• noun (Mus.) Difference in pitch between any two tones.
• noun coming or happening with intervals between; now and then.
• noun (Mus.) an interval increased by half a step or half a tone.

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

• noun A distance in space.
• noun A period of time.
• noun music The difference (a ratio or logarithmic measure) in pitch between two notes, often referring to those two pitches themselves (otherwise known as a dyad).
• noun mathematics A connected section of the real line which may be empty or have a length of zero.
• noun chiefly UK An intermission.
• noun sports half time, a scheduled intermission between the periods of play
• noun cricket Either of the two breaks, at lunch and tea, between the three sessions of a day's play

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

• noun a definite length of time marked off by two instants
• noun the difference in pitch between two notes
• noun a set containing all points (or all real numbers) between two given endpoints
• noun the distance between things