Bottom Of One's Heart
Bottom Of My Heart
adverb, noun
The heart bottom is the bottom of one's heart. Do you want to learn kanji? Do you want to learn it from 心底? Okay, fine, you can move onto the reading then.
This word uses the on'yomi reading for the first kanji and the kun'yomi reading for the second kanji. You've learned them both already, so you should be able to read this too!
コウイチの不治の病が治って、心底うれしいよ。
I'm sincerely happy that Koichi's incurable disease actually has been cured.
コウイチには心底からきらわれていると思います。
I think Koichi hates me from the bottom of his heart.
新しい部署、優しい人がいっぱいで、心底ホッとしたよ。
There are a lot of nice people in my new department and I feel tremendously relieved.