What Is an Explanatory Essay?

The definition

An explanatory essay explains a subject to a reader who does not already understand it, without arguing for a position. Its measure is clarity: by the end, the reader should understand how something works, what happened, or what a term means — and should not be able to tell what you personally think about it.

That last clause is the entire form, and it is the one thing to hold onto if you remember nothing else from this page. The moment you start steering the reader towards a judgement, you are writing a different essay from the one you were set.

Explanatory, informative, expository: which is which

These three words name the same form in most courses, and the differences between them are conventions of vocabulary rather than of writing.

Expository is the broadest of the three. Used strictly, it is the family that includes process essays, definition essays, compare-and-contrast and cause-and-effect — anything whose job is to set something out rather than to argue it.

Informative and explanatory both name the straightforward explain-this-subject version, and are used interchangeably. Where people draw a line, it is usually that informative writing *presents* information while explanatory writing accounts for *how or why* something is the case — explaining a mechanism rather than reporting a state of affairs. That distinction is real enough to be worth knowing and too soft to build an essay on.

If your brief uses one word and your textbook another, they almost certainly mean the same assignment. Write the form, not the label.

There is one context where “explanatory” is a specific term rather than a loose one. Several school curricula, including the US Common Core standards, divide student writing into three types — argument, informative/explanatory, and narrative. If your assignment comes from that framework, “explanatory” means the non-argument, non-story category, and the thing being assessed is whether you can organise information clearly without sliding into persuasion.

Read the verb in the prompt

The faster way to know which essay you have been set is to look at the instruction verb, which is more reliable than the noun.

Explanatory territory: explain, describe, outline, summarise, illustrate, trace, define, account for, compare.

Argumentative territory: argue, evaluate, assess, justify, to what extent, critically discuss, defend.

“Discuss” sits between them and is the one that catches people out. In most UK and Commonwealth marking it expects a position by the end; in much US school usage it does not. If your brief says discuss and you are unsure, ask — guessing wrong here costs more marks than anything else on this page.

It still needs a thesis — a different kind

The question people arrive with is whether an explanatory essay has a thesis. It does, but not an arguable one.

What it has is a controlling idea: a sentence stating what the essay will make clear and in what order, without asserting that anyone should believe something. It still has to be specific, and it still has to predict the body paragraphs.

“This essay is about the 1918 flu pandemic” is a topic label and tells a reader nothing the title did not.

“The 1918 pandemic spread in three distinct waves, each shaped by troop movements, press restrictions and the limits of contemporary medicine” is a controlling idea — nobody disagrees with it, and it tells you exactly what is coming.

The companion piece in this blog, *what is an informative essay*, goes through this distinction, the full structure, topics that work, and the mistakes, in considerably more detail. If you are about to write one, read that next — this page exists mainly to answer which word means what.

The three mistakes specific to this form

Arguing by accident. The failure that defines the form. Words like “unfortunately”, “should”, “sadly”, “clearly” and “shockingly” smuggle in a position. Search your draft for them and decide, each time, whether you meant to take a side. Usually you did not.

Listing instead of explaining. A paragraph that recites facts has described; a paragraph showing how the facts relate has explained. After each sentence, ask whether the reader could now predict something they could not predict before.

No organising principle. Explanatory essays drift more than argumentative ones because nothing forces the order. Choose one before drafting — chronological for events, process order for mechanisms, category order for subjects with distinct parts — and say which you are using to yourself.