The term that best describes the main idea of a piece of writing is "theme." The theme encapsulates the central message or underlying meaning that the author conveys through the narrative, characters, and events. It serves as a guiding principle that ties together various elements of the text, allowing readers to grasp its overall significance.
central point
short musical idea
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Creative writing allows for self expression and allows the writer to go outside the bounds of the norms. Expository writing explains, informs, describes, etc. Its primary purpose is to deliver information about an issue, subject, method, or idea.
The Pilgrims found themselves in a hostile environment with only their religious faith to sustain them
central point
The narrator purpose in writing this proposal is to persuade the reader to agree with their idea or suggestions and to take action on a particular issue or problem being addressed.
the best day for writing is whenever you spring up an idea, and write it.
short musical idea
he proposes a solution to the problem of children becoming a burden to their parents and the country
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Live life to the fullest.
The concluding paragraph summarizes the main points of the writing and reinforces the main idea or argument. It gives closure to the piece, leaving the reader with a final thought or impression.
The union shall last forever
an idea that is supported by many different experiments
Containment
Secularism