columnsep

Columnsep is a length parameter used in TeX and LaTeX to control the horizontal space between columns on a page that uses multiple columns. In standard LaTeX layouts or in environments provided by packages such as multicol or multicols, text is arranged in parallel columns, and columnsep defines the gap between the right edge of one column and the left edge of the next. It is a glue-type length, meaning its effective width can stretch or shrink to help justify the layout within the available text area.

The value of columnsep is independent of the width of an individual column, which is given by columnwidth. The total width occupied by two adjacent columns plus the separation must fit within the page’s text area after margins are accounted for. Defaults for columnsep vary by document class and layout, but the setting can be changed to suit readability or design needs.

To adjust columnsep, a document author can set the length directly, for example with a command like setlength{\columnsep}{<length>} in the preamble or within the document. The exact syntax depends on the TeX dialect being used. It is common to customize column spacing to improve readability in two-column or multi-column formats.

There is also a related parameter, columnseprule, which controls the width of a vertical line drawn between columns if desired. The two parameters together determine both the visual separation and any separating rule between columns. Columnsep interacts with overall layout and balancing, especially in narrow columns or intensive documents.