Respectfully means in a way that shows proper regard. Respectfully disagree, respectfully submitted, treat them respectfully.
I respectfully disagree is a formula that softens a flat contradiction, and it usually precedes a very firm one. Respectfully yours is a formal letter ending and is more distant than sincerely, which is why it appears in official correspondence.
1adverbrespectfullyIn a way that shows proper regard.
“The students stood respectfully as the old soldier walked onto the stage.”
respectfully is a manner.
From respectful + -ly.
Etymology from Wiktionary, CC BY-SA