na-adjective
Describes something that is at the center of an activity, group, or concept; often used in phrases like 中心的な役割 (central role) or 中心的人物 (key person).
彼はプロジェクトの中心的なメンバーだ。
He is a central member of the project.
この問題は議論
This issue became the central theme of the discussion.