expression, adverb
in all sincerity; truthfully; honestly
Emphatic adverbial phrase expressing genuine feeling or truthfulness, stronger than まことに alone.
See also: まことに
誠にもって申し訳ございません。
I am truly very sorry.
まことにもってありがたいお話です。
It is a truly appreciated offer.
まことに is a simpler adverb meaning 'truly' or 'really'; まことにもって is more emphatic and formal, often used in apologies or expressions of gratitude.
Derived from まことに (truly) with the emphatic particle もって added for intensification.