What typically needs a full sentence to be completely defined?

A main idea typically requires a full sentence for its complete definition because it serves as a comprehensive statement encapsulating the central point or argument of a text. It conveys the essence of what the author intends to communicate, summarizing the overall message or primary focus of a passage or work. By expressing the main idea in a full sentence, clarity is achieved, allowing readers to grasp the fundamental concept more readily.

In contrast, a topic can often be expressed in a single word or a short phrase, as it represents a broader subject area without the necessary specificity that a sentence provides. A theme, while it can be nuanced and complex, is typically an underlying message or moral conveyed through the narrative and can sometimes be articulated in a concise statement without requiring full sentence structure. Details usually refer to specific pieces of information or evidence that support the main idea and can often be communicated with simple facts or phrases rather than full sentences. This distinction highlights the importance of the main idea in ensuring a complete understanding of a text's purpose or argument.