Refers to the innermost essential part of something, often used metaphorically for the vital core of an idea, matter, or being.
Used for the central point or focal area of an organization, activity, or system.
bottom of one's heart; innermost feelings
Emphasizes the deepest, most sincere part of one's emotions or thoughts; often used in expressions like 心髄から (from the bottom of one's heart).
His words came from the bottom of his heart.
The core of this problem lies in a lack of trust.
That research institute has become the hub of research in this field.