5.20 Manipulating Type Size and Vertical Spacing

These concepts were introduced in Page Geometry. The height of a font’s tallest glyph is one em, which is equal to the type size in points.⁸² A vertical spacing of less than 120% of the type size can make a document hard to read. Larger proportions can be useful to spread the text for annotations or proofreader’s marks. By default, GNU troff uses 10 point type on 12 point spacing. Typographers call the difference between type size and vertical spacing leading.⁸³