Glyph

Visual textual information is conveyed through glyphs, graphic objects usually mapped onto Characters. However many characters may map onto the same glyph (e.g. Helvetica "l" ("ell") and "I" (capital "I"). And may characters (e.g. "a" may have different glyphs).

Optical Character Recognition involves trying to work out the character from the glyph - this may be difficult or ambiguous.

http://en.wikipedia.org/wiki/Glyph