Leading in the context of "Letter spacing"

In typography, the point is the smallest unit of measure. It is used for measuring font size, leading, and other items on a printed page. The size of the point has varied throughout printing's history. Since the 18th century, the size of a point has been between 0.18 and 0.4 millimeters. Following the advent of desktop publishing in the 1980s and 1990s, digital printing has largely supplanted the letterpress printing and has established the desktop publishing (DTP) point as the de facto standard. The DTP point is defined as 1⁄72 of an inch (or exactly 0.3527 mm) and, as with earlier American point sizes, is considered to be 1⁄12 of a pica.

In metal type, the point size of a font describes the height of the metal body on which that font's characters were cast. In digital type, letters of a computer font are designed around an imaginary space called an em square. When a point size of a font is specified, the font is scaled so that its em square has a side length of that particular length in points. Although the letters of a font usually fit within the font's em square, there is not necessarily any size relationship between the two, so the point size does not necessarily correspond to any measurement of the size of the letters on the printed page.

In typography, the body height or point size refers to the height of the space in which a glyph is defined.

Originally, in metal typesetting, the body height or the font (or point) size was defined by the height of the lead cuboid (metal sort) on which the actual font face is moulded. The body height of a metal sort defined the point size, and was usually slightly larger than the distance between the ascender and descender to allow additional space between the lines of text. More space might be achieved by inserting thin long pieces of lead between the lines of text (that is leading).

In page layout and illustration, white space (or often negative space) is the portion of a page left unmarked: margins, gutters, and space between columns, lines of type, graphics, figures, or objects drawn or depicted. It is not necessarily actually white if the background is of a different colour. The term arises from graphic design practice, where printing processes generally use white paper.White space may be affirmatively an element of design rather than just space left blank.

When space is at a premium, such as in some types of magazine, newspaper, and yellow pages advertising, white space is restricted in order to get as much information onto the page as possible. A page full of text or graphics with very little white space may appear cluttered, and be difficult to read. Some designs compensate for restricted white space by use of leading and typeface. Extensive white space may be left intentionally, with the purpose of giving an appearance deemed classic, elegant, or rich.