What is the difference between an essay, a report and a dissertation?
They differ in structure, purpose and how the reader is expected to use them — and marks are lost mainly by writing one in the shape of another.
Essay. A continuous argument in prose. No headings in many disciplines, no bullet points, no sections. Structure is introduction, body and conclusion, with the argument carried by paragraphing and connective writing.
The purpose is to make and defend a position. An essay that summarises what various people think without arriving at a judgement has missed the form. The reader reads it from start to finish.
Report. Sectioned and headed, designed to be navigated rather than read through. A typical structure is abstract or executive summary, introduction, methods, results, discussion, conclusion, recommendations, appendices.
The purpose is to present findings and enable a decision. A reader may read only the summary and the recommendations. Bullet points, tables and figures are appropriate and expected.
The executive summary is the part most people write badly: it should contain the actual conclusions, not a description of what the report will discuss.
Dissertation or thesis. An extended independent research project — typically the culminating piece of a degree. It combines both forms: sectioned like a report, argued like an essay.
Its distinguishing requirement is a literature review establishing what is known and identifying a gap, followed by original work addressing it. The research question governs everything, and the most common failing is a project without a clear one.
The practical differences in writing:
Voice. Essays argue; reports inform; dissertations do both, with disciplinary conventions on first person varying considerably.
Signposting. Reports use headings; essays use sentences.
Length management. A dissertation needs planning and drafting over months, and word counts are usually enforced strictly.
Always read the brief and the marking criteria, which override generic advice.