The adjective ENDEARING derives from the verb TO ENDEAR and means making a person or something liked by others, often unique or different:
Her cheerful personality was very endearing.
Do I have any endearing qualities at all?
I find your folks so endearing.
I don’t understand how you can find this endearing.
The adverb deriving from this adjective is ENDEARINGLY:
She’s an endearingly cheerful girl.
Life in this little village is so endearingly slow.
Yes, he is a little eccentric, but endearingly eccentric, I would say.
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