noun
subtopic; subtheme
A secondary or subordinate topic within a larger theme or discussion. Common in academic, business, and planning contexts.
wasei-eigo (Japanese-coined English), from subtheme
会議では、メインテーマの下に三つのサブテーマが設定された。
At the meeting, three subtopics were set under the main theme.
この論文は、環境問題という大きなテーマの中のサブテーマ
This paper deals with a subtopic within the larger theme of environmental issues.