slowly
adv.at a low speed. You use this when something takes a long time to happen or move.
adv.at a low speed or pace; not quickly. Often used to modify verbs of motion or processes that occur over an extended duration.
“Please speak slowly so I can understand you.”
“The old car moved slowly up the steep hill while the engine made a loud noise.”
“The glacier retreats slowly over decades, leaving behind a transformed landscape that reveals the immense power of gradual geological shifts.”
Manner adverb — typically placed after the main verb or at the end of the clause.
While 'slow' is sometimes used as an adverb in informal speech, 'slowly' is the standard form required in most contexts.
Usage slowly develop
From Middle English slowly, slowli, slouli, slowliche, from Old English slāwlīċe (“slowly; sluggishly”), equivalent to slow + -ly. Compare Old Norse slæliga, sljóliga.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.