adverb taking the 'to' particle
very deeply; profoundly
Describes a deep state, often used with verbs like 眠る (sleep), 考える (think), or 感謝する (thank). The adverbial form 深々と is common.
He is sleeping very deeply.
I felt profoundly grateful for those words.
Kana spelling is sometimes used, especially in casual writing or when avoiding kanji.
Full kanji repetition form; less common than 深々.
Reduplication of 深 (ふか, 'deep') with the adverbial suffix 々, yielding an emphatic adverbial form.