深ふか々ぶか

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.

• 彼かれは深ふか々ぶかと眠ねむっている。

  He is sleeping very deeply.

• その言こと葉ばに深ふか々ぶかと感かん謝しゃした。

  I felt profoundly grateful for those words.