Promptly means without any delay. The reply that comes the same afternoon, the bill paid the week it arrives.
It has a second use that surprises learners, because promptly also means exactly at a stated time, as in the meeting began promptly at nine. And there is a third, faintly comic use in storytelling, where promptly marks something happening immediately and usually badly — he stood up and promptly fell over. That last sense is very common in speech. The adjective prompt covers the same ground.
1adverbpromptlyWithout delay.
“She answered the letter promptly.”
2adverbexactlyExactly at the stated time.
“The train left promptly at six.”
3adverbimmediatelyImmediately afterwards, often unfortunately.
“He was given the vase and promptly dropped it.”
Latin
prōmptus — visible, apparent, evident
Middle French
prompt
Middle English
prompte
English
prompt
English, today
promptly
Built from
From prompt + -ly. prompt The adjective is from Middle English prompte, from Middle French prompt and its etymon Latin prōmptus (“visible, apparent, evident”), past participle of prōmō (“to take or bring out or forth, produce, bring to light”), from prō (“forth, forward”) + emō (“to take, acquire, buy”). a doublet of pronto. The verb is from Middle English prompen, apparently from the adjective. The noun is from the verb.
Etymology from Wiktionary, CC BY-SA