This is the 305th most frequent Korean word.
충분히
"Sufficiently" or "enough."
충분히 is used here to describe the extent of an action, specifically sleeping adequately.
충분히 자야 건강을 유지할 수 있습니다.
You need to sleep enough to maintain your health.
충분히 emphasizes the preparedness to suggest it was adequate or thorough.
그는 충분히 준비하고 시험을 보았습니다.
He prepared sufficiently and then took the exam.
충분히 is used to describe the extent of discussion, indicating it was exhaustive or satisfactory.