in physical comfort
"she could have been lying comfortably in bed getting the same relief"
in financial comfort
"They live well"
"she has been able to live comfortably since her husband died"
In a comfortable manner.
"She sat comfortably in her favorite armchair and read the book."
The word comfortably is formed by adding the suffix -ly to the adjective comfortable. It entered English as an adverb describing a state of ease derived from its root meaning.