Which term is usually expressed in a few words at most?

The term that is usually expressed in a few words at most is "Topic." A topic denotes the subject or focus of a piece of writing or discussion and is typically succinct, often consisting of just a noun or a simple phrase. It serves as the foundation for further exploration within a text, guiding the reader about what to expect.

In contrast, other options, such as the main idea, generally encapsulates the primary point or argument of a text and may require a more extended explanation. The theme is a broader concept that often involves complex ideas or interpretations and might be expressed in several words or sentences. Supporting details provide evidence or examples to reinforce the main idea and typically involve multiple sentences for clarity and context. Therefore, the simplicity and brevity of a topic make it easier to recognize and articulate in just a few words.