1.  The longest, or longer, dimension of any object, in distinction from breadth or width; extent of anything from end to end; the longest line which can be drawn through a body, parallel to its sides; as, the length of a church, or of a ship; the length of a rope or line. [1913 Webster]

2.  A portion of space or of time considered as measured by its length; -- often in the plural. [1913 Webster]
"Large lengths of seas and shores." [1913 Webster]
"The future but a length behind the past." [1913 Webster]

3.  The quality or state of being long, in space or time; extent; duration; as, some sea birds are remarkable for the length of their wings; he was tired by the length of the sermon, and the length of his walk. [1913 Webster]

4.  A single piece or subdivision of a series, or of a number of long pieces which may be connected together; as, a length of pipe; a length of fence. [1913 Webster]

5.  Detail or amplification; unfolding; continuance as, to pursue a subject to a great length. [1913 Webster]
"May Heaven, great monarch, still augment your bliss
With length of days, and every day like this." [1913 Webster]

6.  Distance. [1913 Webster]
"He had marched to the length of Exeter." [1913 Webster]

   To lengthen. Shak. [1913 Webster]

length, n.
1 measurement or extent from end to end; the greater of two or the greatest of three dimensions of a body.
2 extent in, of, or with regard to, time (a stay of some length; the length of a speech).
3 the distance a thing extends (at arm's length; ships a cable's length apart).
4 the length of a horse, boat, etc., as a measure of the lead in a race.
5 a long stretch or extent (a length of hair).
6 a degree of thoroughness in action (went to great lengths; prepared to go to any length).
7 a piece of material of a certain length (a length of cloth).
8 Prosody the quantity of a vowel or syllable.
9 Cricket a the distance from the batsman at which the ball pitches (the bowler keeps a good length). b the proper amount of this.
10 the extent of a garment in a vertical direction when worn.
11 the full extent of one's body.

Idiom:
at length
1 (also at full or great etc. length) in detail, without curtailment.
2 after a long time, at last.

Etymology:
OE lengthu f. Gmc (as LONG(1))

N  space, extension, extent, superficial extent, expanse, stretch, hyperspace, room, scope, range, field, way, expansion, compass, sweep, swing, spread, dimension, length, distance, size, volume, hypervolume, latitude, play, leeway, purchase, tolerance, room for maneuver, spare room, elbow room, house room, stowage, roomage, margin, opening, sphere, arena, open space, free space, void, waste, wildness, wilderness, moor, moorland, campagna, abyss, unlimited space, infinity, world, ubiquity, length and breadth of the land, proportions, acreage, acres, acres and perches, roods and perches, hectares, square miles, square inches, square yards, square centimeters, square meters, yards (clothing), ares, arpents, spacious, roomy, extensive, expansive, capacious, ample, widespread, vast, world-wide, uncircumscribed, boundless, shoreless, trackless, pathless, extended, extensively, wherever, everywhere, far and near, far and wide, right and left, all over, all the world over, throughout the world, throughout the length and breadth of the land, under the sun, in every quarter, in all quarters, in all lands, here there and everywhere, from pole to pole, from China to Peru, from Indus to the pole, from Dan to Beersheba, from end to end, on the face of the earth, in the wide world, from all points of the compass, to the four winds, to the uttermost parts of the earth.

N  distance, space, remoteness, farness, far- cry to, longinquity, elongation, offing, background, remote region, removedness, parallax, reach, span, stride, outpost, outskirt, horizon, aphelion, foreign parts, ultima Thule, ne plus ultra, antipodes, long range, giant's stride, dispersion, length, cosmic distance, light-years, distant, far off, far away, remote, telescopic, distal, wide of, stretching to, yon, yonder, ulterior, transmarine, transpontine, transatlantic, transalpine, tramontane, ultramontane, ultramundane, hyperborean, antipodean, inaccessible, out of the way, unapproached, unapproachable, incontiguous, far off, far away, afar, afar off, off, away, a long way off, a great way off, a good way off, wide away, aloof, wide of, clear of, out of the way, out of reach, abroad, yonder, farther, further, beyond, outre mer, over the border, far and wide, over the hills and far away, from pole to pole, to the uttermost parts, to the ends of the earth, out of hearing, nobody knows where, a perte de vue, out of the sphere of, wide of the mark, a far cry to, apart, asunder, wide apart, wide asunder, longo intervallo, at arm's length, distance lends enchantment, it's a long long way to Tipperary, out of sight, out of mind.

N  length, longitude, span, mileage, distance, line, bar, rule, stripe, streak, spoke, radius, lengthening, prolongation, production, protraction, tension, tensure, extension, line, nail, inch, hand, palm, foot, cubit, yard, ell, fathom, rood, pole, furlong, mile, league, chain, link, arpent, handbreadth, jornada, kos, vara, astronomical unit, AU, light- year, parsec, nanometer, nm, micron, micrometer, millimicron, millimeter, mm, centimeter, cm, meter, kilometer, km, pedometer, perambulator, scale, long, longsome, lengthy, wiredrawn, outstretched, lengthened, sesquipedalian, interminable, no end of, macrocolous, linear, lineal, longitudinal, oblong, as long as my arm, as long as today and tomorrow, unshortened &c (shorten), lengthwise, at length, longitudinally, endlong, along, tandem, in a line, in perspective, from end to end, from stem to stern, from head to foot, from the crown of the head to the sole of the foot, from top to toe, fore and aft.

arm's length, at arm's length, at length, bishop's length, body length, cable length, cable's length, focal length, length of service