grapheme

noun3

1. •
   A fundamental unit of a writing system, corresponding to (for example) letters in the English alphabet or jamo in Korean hangul.

   • For instance, it is convenient to refer to a single Chinese character as being a grapheme in some contexts. — 2000
2. •
   A sequence of one or more code points that are processed and displayed as a single graphical unit of a writing system.

   • Even so, it's important for Unicode-friendly applications to deal with text in their user interfaces as a series of graphemes and not as a series of Unicode code points […] — 2003
3. •
   In alphabetic writing, the shortest group of letters composing a phoneme.

   • The term for a letter or combination of letters which represents a particular sound is a “grapheme”. Languages like Italian and Serbo-Croatian have very simple “grapheme–phoneme conversion” rules. — 1987