having considerable linear extent in space

a long distance; a long handle.

having considerable duration in time

a long conversation; a long while.

extending, lasting, or totaling a number of specified units

eight miles long; eight hours long.

containing many items or units

a long list.

requiring a considerable time to relate, read, etc.

a long story.

extending beyond normal or moderate limits

a long, boring speech.

experienced as passing slowly, because of the difficulty, tedium, or unpleasantness involved

long years of study.

reaching well into the past

a long memory.

the longer of two or the longest of several

the long way home; a brick with the long side exposed.

taking a long time; slow

He's certainly long getting here.

forward-looking or considering all aspects; broad

to take a long view of life.

intense, thorough, or critical; seriously appraising

a long look at one's past mistakes.

having an ample supply or endowment of something (often fol. by on )

to be long on advice; to be long on brains.

having a considerable time to run, as a promissory note.

Chiefly Law . distant or remote in time

a long date.

extending relatively far

a man with a long reach.

being higher or taller than usual

long casement windows.

being against great odds; unlikely

a long chance.

(of beverages) mixed or diluted with a large amount of soda, seltzer, etc.

highballs, collinses, and other long drinks.

(of the head or skull) of more than ordinary length from front to back.

Phonetics .

lasting a relatively long time

Feed has a longer sound than feet or fit.

belonging to a class of sounds considered as usually longer in duration than another class, as the vowel of bought as compared to that of but, and in many languages serving as a distinctive feature of phonemes, as the ah in German Bahn in contrast with the a in Bann, or the tt in Italian fatto in contrast with the t in fato ( opposed to short ).

having the sound of the English vowels in mate, meet, mite, mote, moot, and mute, historically descended from vowels that were long in duration.

Prosody . (of a syllable in quantitative verse) lasting a longer time than a short syllable.

Finance . holding or accumulating stocks, futures, commodities, etc., with the expectation of a rise in prices

a long position in chemicals.

Gambling .

marked by a large difference in the numbers of the given betting ratio or in the amounts wagered

long odds.

of or pertaining to the larger amount bet.

Ceramics . (of clay) very plastic; fat.

a comparatively long time

They haven't been gone for long. Will it take long?

something that is long

The signal was two longs and a short.

a size of garment for men who are taller than average.

a garment, as a suit or overcoat, in this size

The shorts and the longs are hung separately.

Finance . a person who accumulates or holds stocks or commodities with the expectation of a rise in prices.

Music . longa.

for or through a great extent of space or, esp., time

a reform long advocated.

for or throughout a specified extent, esp. of time

How long did he stay?

(used elliptically in referring to the length of an absence, delay, etc.)

Will she be long?

throughout a specified period of time (usually used to emphasize a preceding noun)

It's been muggy all summer long.

at a point of time far distant from the time indicated

long before.

as long as

provided that

As long as you can come by six, I'll be here.

seeing that; since

As long as you're going to the grocery anyway, buy me a pint of ice cream.

Also, so long as. during the time that; through the period that

As long as we were neighbors, they never invited us inside their house.

before long

soon

We should have news of her whereabouts before long.

the long and the short of

the point or gist of; substance of

The long and the short of it is that they will be forced to sell all their holdings. Also, the long and short of.