What is the primary function of a thesis statement in an essay?

The primary function of a thesis statement in an essay is to clearly express the main idea. It serves as a roadmap for the writer and guides the reader by presenting the central argument or point the essay will make. A well-crafted thesis statement encapsulates the essence of the argument in a concise manner, allowing the reader to understand what to expect in the forthcoming sections of the essay. It also establishes the writer's position on the topic, which can then be supported and elaborated upon throughout the essay.

The other choices do not capture the primary function of a thesis statement. While summarizing the entire essay, entertaining the reader, or providing background information may be important aspects of writing, they do not represent the core role of a thesis statement, which is strictly to articulate the main idea effectively.