Blockquotes and rules

A blockquote marks text as someone else's words: a passage from a paper you are discussing, a definition quoted from a textbook, a remark from a referee. A horizontal rule marks a break in the text itself. Both are plain CommonMark, so they work the same here as anywhere else you write Markdown.

Blockquotes

Start each line with > and a space:

> Mathematics is the art of giving the same name to different things.
>
> --- Henri Poincaré

The empty > line keeps the attribution inside the same quote as a second paragraph. Without it, the attribution would join the quoted sentence. Three hyphens (---) become an em dash, so the attribution line gets the usual typographic dash without you having to type it.

Only the first line needs the marker

A paragraph that has started inside a quote continues on the lines that follow, even without >. CommonMark calls this lazy continuation:

> The theory of probabilities is at bottom nothing
but common sense reduced to calculus.

It helps when you paste a long passage. The next block (a new paragraph, a list, a heading) still needs its own >, so for anything longer than one paragraph, prefix every line. That is also the form the editor writes.

What a quote can contain

A blockquote holds any block content: several paragraphs, lists, code, display maths and other quotes. Nest a quote by adding another >:

> The referee writes:
>
> > The second lemma assumes $f$ is continuous, but only uses that
> > $f$ is bounded on $[0, 1]$.
>
> Both remarks are addressed in the revised version:
>
> 1. The hypothesis of Lemma 2 is weakened to boundedness.
> 2. The proof of $\displaystyle\int_0^1 f \le \sup f$ now cites it.

Quote only what you are discussing. A quote that runs for pages is usually a sign the text belongs in an appendix or an attachment instead.

A quote, a callout, or an epigraph?

Three constructs look similar on the page and mean different things:

Choose by meaning, not by look. A screen reader, a search engine and an export to LaTeX each treat the three differently, and they rely on you having picked the one that says what the text is.

GitHub alerts are not callouts here

GitHub renders > [!NOTE] as a coloured callout. Here it stays an ordinary blockquote whose first line reads [!NOTE]. When you import a document written that way, the importer converts it to the :::note form; when you type it by hand, write the admonition directly.

Horizontal rules

Three or more hyphens alone on a line make a horizontal rule, a break between two parts of the text:

The first part of the argument ends here.
 
---
 
The second part starts from a different assumption.

Asterisks (***) and underscores (___) make the same rule. Spaces between the characters are allowed (- - -).

Keep a blank line above it

Put a blank line before a hyphen rule. Directly under a line of text, --- does not make a rule: it turns that text into a heading (the old "underline" heading form). If a paragraph unexpectedly became a heading, a missing blank line above --- is almost always why. The *** form has no such trap.

Rules and headings

A rule says "a break in the text" and nothing more. It has no title, no anchor, and no entry in the table of contents. When the new part has a subject you could name, a heading is better: readers can see the structure and link to it. Rules suit breaks that have no name, such as a change of scene in an essay or a pause before a closing remark. In a book, a rule is the scene break and is typeset as one.