Forever means for all time, without ending. Nothing lasts forever. I will remember it forever. It is the ordinary word for permanence and it is used far more often as an exaggeration than as a fact.
That exaggerated use is worth naming: it took forever means it took a long time, and it is entirely standard. There is a second, distinct sense with a continuous verb — he is forever losing his keys — meaning constantly and annoyingly, and there the word carries no idea of eternity at all. British English also writes it as two words, for ever, in the literal sense, keeping forever for the annoyed one; American English uses one word throughout, and the one-word form is now commoner everywhere.
1adverbforeverFor all time; permanently.
“The photographs are gone forever.”
synonyms: always, eternally, permanently
2adverblongFor a very long time, said with impatience.
“That queue took forever.”
3adverbconstantlyConstantly and annoyingly.
“He is forever leaving the door open.”
Too few real examples of this word to estimate which sense is commonest.
forever is a stretch of time.
Also accepted in games: eternally
Middle English
for ever
English, today
forever
From for. for ever, from Middle English for ever, for evere. by surface analysis, en + for + ever. late 14c., and late 17c. as one word. Noun 1858.
Etymology from Wiktionary, CC BY-SA