Leading

In typography, leading is an amount of space included above and below text to provide spacing between lines. Historically, in physical typesetting, pieces of actual lead were used to implement this spacing, which is where the name comes from.

In CSS, typographic leading is the difference between the content height and the line-height, generally set by the line-height property. Leading set via line-height provides spacing between lines, which can be negative. The space is distributed equally above and below the text, which is referred to as half-leading.

The area of a font above the cap baseline is referred to as the over edge. The area below the alphabetic baseline is referred to as the under edge. Likewise, the half-leading above and below a line is referred to as the over leading and under leading, respectively.