Microsoft Word can automatically count the lines in a document and display the appropriate number beside each line of text. This is useful if you need to refer to specific lines in a document, such as a script or legal contract.

By default, Word numbers every line in a document (except those in tables (table: One or more rows of cells commonly used to display numbers and other items for quick reference and analysis. Items in a table are organized into rows and columns.), footnotes, endnotes, text boxes (text box: A movable, resizable container for text or graphics. Use text boxes to position several blocks of text on a page or to give text a different orientation from other text in the document.), frames (frame: A container that you can resize and position anywhere on the page. To position text or graphics that contain comments, footnotes, endnotes, or certain fields, you must use a frame instead of a text box.), and headers and footers (header and footer: A header, which can consist of text or graphics, appears at the top of every page in a section. A footer appears at the bottom of every page. Headers and footers often contain page numbers, chapter titles, dates, and author names.)). However, you can choose which line numbers to display. For example, include line numbers in all or part of the document. Or include line numbers at intervals, such as every tenth line (10, 20, 30, and so on).
If you don't want Word to count specific lines, such as a heading or a blank line, you can skip line numbers for these items and continue numbering the following lines.