Adjusting the average distance between letters in a block of text to fit more or less text into the given space or to improve legibility. Kerning allows adjustments between individual letters; letterspacing is applied to a block of text as a whole. Letterspacing is sometimes referred to as tracking or track kerning.
Adobe Glossary of typographic terms
Extra space inserted between letters in a word.
Cel Mai folosit cuvant: extra | Domeniu Aplicare : Tipografie si design | Caractere: 39 Cuvinte: 9 | Limba: Engleza | Sursa typographia glossary