Grapheme

A minimal functional unit of a writing system, such as a letter, character, or punctuation mark. A grapheme may consist of one or several written symbols.

Phoneme: The smallest sound unit that can distinguish meaning in a language. Graphemes may represent phonemes, but written units and sound units are not the same.
Grapheme–phoneme correspondence: A relation between written units and the speech sounds they represent. Alphabetic graphemes often map to phonemes, though the mapping may be irregular or context-dependent.
Latin alphabet: The alphabet used to write English and many other languages. Its letters provide familiar examples of graphemes, with sound values varying across languages.
Graph (linguistics): A minimal written form distinguished by its shape, regardless of linguistic function. A graph is a physical or visual unit; a grapheme is defined by its role in a writing system.
Morpheme: The smallest linguistic unit that carries meaning or grammatical function. A grapheme can spell part or all of a morpheme without itself carrying that meaning.
Digraph (orthography): A pair of letters that represents one sound or another single orthographic unit. Some graphemes consist of multiple letters functioning together, as in English sh.
Hangul: The Korean writing system, whose alphabetic letters are arranged into syllable blocks. Hangul separates letter-level graphemes from the syllable blocks formed in writing.
Letter: A conventional written symbol used as a unit in an alphabet. Letters are common graphemes, but not every grapheme is a single letter.
Glyph: A particular visual form used to represent a character or symbol. A grapheme is a functional writing unit; a glyph is one of its visible forms.
Trigraph (orthography): A sequence of three letters that represents one sound or orthographic unit. It illustrates that a grapheme need not be a single written character.

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