In the same way that the
surface forms of
phonemes are speech sounds or
phones (and different phones representing the same phoneme are called
allophones), the surface forms of graphemes are
glyphs (sometimes
graphs), namely concrete written representations of symbols (and different glyphs representing the same grapheme are called
allographs). Thus, a grapheme can be regarded as an
abstraction of a collection of glyphs that are all functionally equivalent. For example, in written English (or other languages using the
Latin alphabet), there are two different physical representations of the
lowercase Latin letter "a": "a" and "ɑ". Since, however, the substitution of either of them for the other cannot change the meaning of a word, they are considered to be allographs of the same grapheme, which can be written . Similarly, the grapheme corresponding to "Arabic numeral zero" has a unique semantic identity and Unicode value but has variations such as how circular it is drawn or even the
slashed zero form. Italic and bold face forms are also allographic, as is the variation seen in
serif (as in
Times New Roman) versus
sans-serif (as in
Helvetica) forms. There is some disagreement as to whether capital and lower case letters are allographs or distinct graphemes. Capitals are generally found in certain triggering contexts that do not change the meaning of a word: a proper name, for example, or at the beginning of a sentence, or all caps in a newspaper headline. In other contexts, capitalization can determine meaning: compare, for example
Polish and
polish: the former is a language, the latter is for shining shoes. Some linguists consider
digraphs like the in
ship to be distinct graphemes, but these are generally analyzed as sequences of graphemes. Non-stylistic
ligatures, however, such as , are distinct graphemes, as are various letters with distinctive
diacritics, such as . Identical glyphs may not always represent the same grapheme. For example, the three letters , and appear identical but each has a different meaning: in order, they are the Latin letter
A, the Cyrillic letter
Azǔ/Азъ and the Greek letter
Alpha. Each has its own
code point in Unicode: , and . ==Types of grapheme==