Definition:

A letter of the alphabet, a mark of punctuation, or any other individual symbol in a writing system. Adjective: graphemic.

The grapheme has been described as the "smallest contrastive linguistic unit which may bring about a change of meaning" (A.C. Gimson, An Introduction to the Pronunciation of English, 1962).

See also:

• Digraph
• Graphology
• Logograph
• Sign
• Symbol

Etymology:

From the Greek, "writing"

Examples and Observations:

• "The basic unit of written language is the letter. The name grapheme is given to the letter or combination of letters that represents a phoneme. For example, the word 'ghost' contains five letters and four graphemes ('gh,' 'o,' 's,' and 't'), representing four phonemes. There is much more variability in the structure of written language than there is in spoken languages. Whereas all spoken languages utilize a basic distinction between consonants and vowels, there is no such common thread to the world's written languages."
  (Trevor A. Harley, The Psychology of Language: From Data to Theory, 2nd ed. Psychology Press, 2001)

• Phonemes and Graphemes
  "Typically, beginners are taught grapheme-phoneme correspondences when they begin school. These associations are easier to learn if students already know the names of letters, because most letter names include relevant sounds, for example /t/ in tee, and k in kay. . . .
  
  "There are about 40 distinctive phonemes in English, but 70 letters or letter combinations to symbolize phonemes. This makes pronouncing spellings easier than writing correct spellings."
  (Linnea C. Ehri, "Grapheme-Phoneme Knowledge Is Essential for Learning to Read Words in English," Word Recognition in Beginning Literacy, ed. by Jamie L. Metsala and Linnea C. Ehri. Erlbaum, 1998)
• Graphemes and Meaning
  "Graphemes are the smallest units in a writing system capable of causing a contrast in meaning. In the English alphabet, the switch from cat to bat introduces a meaning change; therefore, c and b represent different graphemes. It is usual to transcribe graphemes within angle brackets, to show their special status: <c>, <b>. The main graphemes of English are the twenty-six units that make up the alphabet. Other graphemes include the various marks of punctuation: <.>, <;>, etc., and such special symbols as <@>, <&>, and (£). . . .
  
  "Graphemes . . . may signal whole words or word parts--as with the numerals, where each grapheme <1>, <2>, etc. is spoken as a word that varies from language to language (a logogram). . . . And several of the relationships between words are conveyed by graphology more clearly than by phonology: for example, the link between sign and signature is very clear in writing, but it is less obvious in speech, because the g is pronounced in the second word, but not in the first."
  (David Crystal, How Language Works. Overlook Press, 2005)

• Morphograms
  "Spellings like to, too, two, sea, see, and phrase, frays, multiplied by hundreds of other examples, make for complex grapheme-phoneme correspondences, but the interpretation of written texts does not depend on these correspondences alone. Exploiting other systemic levels of language is equally common and practical. The plural of both dog and cat is uniformly indicated by -s, although it is [dogz] but [kaets]. In the event -s can be understood as indicating the plural morpheme rather than a sound. Accordingly, such spellings are sometimes referred to as morphograms."
  (Florian Coulmas, Writing Systems: An Introduction to Their Linguistic Analysis. Cambridge University Press, 2003)

* Pauline B. Low and Linda S. Siegel, "Spelling and English Language Learning." Instruction and Assessment for Struggling Writers: Evidence-Based Practices, ed. by Gary A. Troia. Guilford Press, 2009)

Pronunciation: GRAF-eem