Synonyms for Forever:

adj.

•eternal (adjective)
everlasting, persistent, unbroken, unceasing, interminable, continual, continuous, indefinite, permanent.
•lasting (adjective)
continuing, endless.
•permanent (adjective)
forever and a day.

adv.

•forever (adverb)
everlastingly, permanently, regularly, world without end, infinitely, always, eternally, evermore, interminably.

adv

•all the time (adverb)
interminably.
•continuously (adverb)
regularly.
•ever (adverb)
everlastingly.

n.

interminable, persistent, protracted, long-drawn-out, lingering, day in day out, everlasting, lengthy, long. •forever (noun)
everlastingly, infinity, always, evermore, forever and a day, eternity, eternally.
•indefinite duration (noun)
age, aeon, era, time, eternity, duration, lapse, span.
•perpetuity (noun)
ceaselessness, permanence, everlastingness, endurance, constancy, lastingness, time immemorial, infinity, endlessness, immortality, perpetuity, interminability, continuousness.

Other synonyms:

lengthy, unceasing, unfailing, long-drawn-out, permanently, continuing, interminable, lingering, protracted. continuous, continual, everlasting, unbroken, indefinite, endless, permanent, persistent. long. •always
always.
•endlessly
interminably.
•Other relevant words:
Aye, everlasting, eternally, infinitely, forever and a day, interminably, unceasing, indefinite, unfailing, always, continual, permanent, endless, permanently, persistent, unbroken, regularly, everlastingly, protracted, interminable, lingering, evermore.

Usage examples for forever

1. You learn things by saying them over and over and thinking about them until they stay in your mind forever and I think it will be the same with Magic. – The Secret Garden by Frances Hodgson Burnett

2. " You are mine, then, now,- now and forever he says, presently. – Rossmoyne by Unknown

3. And for happiness, dear, there is a Forever that is full of it! – The Other Girls by Mrs. A. D. T. Whitney