For or during a long time.

Following a preposition, as for, in, (now archaic and rare) of (formerly also †by, †to). In later use only with indefinite article. Cf. phrases 1.

For a long time; = long, adv.1 1a.

For a long time, for long; lengthily and tediously. Also: slowly, tardily.

For a long time (past, or rarely to come).

In a lasting manner; continually, enduringly, permanently, perpetually, persistently, durably.

Preceding ago or agone: = long, adv.1 2a.

Throughout a long period. Now chiefly in negative contexts. Also occasionally †for long and long, for long together. Also (chiefly with reference…

in length. To a long distance; for a long time. Obsolete.

with the longest: of a very great extent; for a very long time. Obsolete.

hyperbolically.

For some time. rare.

In a chronic manner; inveterately.

colloquial (originally U.S.). For a very long time, esp. for a (seemingly) inordinate amount of time. Cf. sense B. 2.

For some time.

The time during which a war lasts, used first of the 1914–18 war from the term of enlistment ‘for four years or the duration of the war’; esp. in f…

In or over the long term; on a long-term basis.

Astronomy. Over a long period of time.