The definition of a subtopic is something that is part of a broader area of discussion.
If your paper is about poverty and there is a section of your paper devoted specifically to urban poverty, this is an example of a subtopic of your paper.
a topic that is a division of a main topic
One of the divisions into which a main topic may be divided.
- A subject that forms part of a topic.
- The meeting dragged on interminably as topics were divided into subtopics which were divided in to sub-sub-topics, ad infinitum.
From sub- +"Ž topic.