a glossary of typographic terms
This glossary is a work in progress, so please excuse any omissions. If you’d like to help edit this glossary, then send me a message.
Side Bearings (also sidebearings)
The horizontal spaces either side of an individual character or glyph. The spaces either side are referred to as Left Side Bearing (LSB) and Right Side Bearing (RSB). These spaces ensure that characters sit beside one another with an even appearance. Sometimes the term is used to describe the extreme right and left edges of a glyph, including the space either side.
The example below demonstrates negative side-bearings. However, sidebearings can also be positive, and therefore extend beyond the limits of the bounding box seen here.
Short definition from The Complete Manual of Typography:
The space between the outer edge of a character and the edge of its bounding box (digital type) or type block (metal type). The side bearings of two adjoining characters combine to create the letter space between them.