nucleus

1. Origins, structure, and basic meaning

• Structure: 核 has 10 strokes and refers to the central part of a thing or idea.
• Basic usage: 核 is read かく, and 核心, the core of an issue, is read かくしん.

2. Common pitfalls and similar expressions

• A physical or abstract center
  • 原子の核 is an atom's nucleus, while チームワークの核 is the element central to teamwork.
• The heart of a discussion
  • 議論の核心を突いていた means that something was getting to the heart of the discussion.