the longest extent of anything as measured from end to end

the length of a river.

the measure of the greatest dimension of a plane or solid figure.

extent from beginning to end of a series, enumeration, account, book, etc.

a report running 300 pages in length.

extent in time; duration

the length of a battle.

a distance determined by the extent of something specified

Hold the picture at arm's length.

a piece or portion of a certain or a known extent

a length of rope.

the quality or state of being long rather than short

a journey remarkable for its length.

the extent to which a person might or would go in pursuing something

He went to great lengths to get what he wanted.

a large extent or expanse of something.

the measure from end to end of a horse, boat, etc., as a unit of distance in racing

The horse won by two lengths.

Clothing . the extent of a garment related to a point it reaches, as on the wearer's body, the floor, or on a garment used as a standard of measurement (usually used in combination)

an ankle-length gown; a floor-length negligee; a three-quarter-length coat.

Prosody, Phonetics .

(of a vowel or syllable) quantity, whether long or short.

the quality of vowels.

Bridge . the possession of four or more than four cards in a given suit.

Theater Archaic . 42 lines of an acting part. ?

at length

in or to the full extent; completely.

after a time; finally

At length there was a step forward in the negotiations.

go to any length or lengths

to disregard any impediment that could prevent one from accomplishing one's purpose

He would go to any lengths to get his own way.

keep at arm's length. arm 1 ( def. 16 ) .