run on

In typesetting, to run on means to continue text in the same paragraph or line without inserting a line break, paragraph break, or other visual separation. A compositor or typesetter receives copy marked "run on" and sets it as continuous matter, allowing it to flow naturally across line breaks determined only by the measure (column width) rather than by editorial intent to start fresh.

The instruction appears in manuscript markup as "RO" or circled text, signaling that what would normally start a new paragraph should instead join the preceding text. This is common in reference works, tables of contents, and dense technical documents where multiple short thoughts or entries run together for economy of space. The opposite instruction, "break" or "new par," forces the start of a new paragraph regardless of where the previous one ended.

Why the confusion matters

Run on differs from a typographic error (a "run-on sentence") in that it is intentional and markup-driven. A printer or digital compositor executing a run-on instruction is making a deliberate choice about document structure, not overlooking a punctuation problem. However, copy marked for running on must still be grammatically sound; the instruction controls paragraph architecture, not sentence construction.

In digital publishing and word processing, the equivalent is a soft return or inline formatting that keeps lines together without creating a paragraph boundary. The term persists in editorial style guides and copyediting marks even as metal type and hand composition have largely disappeared, because the concept remains essential to controlling the visual and logical flow of printed matter.