graphemes

A grapheme is the smallest unit of a writing system that can distinguish meaning. In linguistic and orthographic terms, a grapheme is the written counterpart of a phoneme, the smallest unit of sound, though a grapheme can have several surface forms and a single form can represent different sounds in different contexts.

In alphabetic systems, graphemes include letters as well as digraphs and trigraphs that function as a single unit for a given sound. The mapping between graphemes and phonemes is called grapheme–phoneme correspondences; it is not always one-to-one. A single phoneme may be written with different graphemes (e.g., /f/ as f or ph), and a grapheme may represent different phonemes depending on context (e.g., c in city vs cope). Graphemes also have allographs—different visual shapes that represent the same underlying grapheme, such as lowercase and uppercase forms or letters with diacritics.

Different writing systems illustrate different uses. English uses an alphabet with discrete graphemes like a, b, c, as well as digraphs like th, ch, sh. Other scripts include logographic systems such as Chinese, where characters are graphemic units that encode morphemes or words rather than phonemes. In Japanese, kanji combines with kana; Korean Hangul composes syllable blocks from graphemic letters.

In digital typography and Unicode, a grapheme cluster is the user-perceived character, often composed of a base letter plus one or more combining marks. Treating clusters as single units is important for text rendering and input.

The concept is central to linguistics, literacy research, orthography design, and computational text processing.