A character is a semiotic sign or symbol, or a glyph - typically a letter, a numerical digit, an ideogram, a hieroglyph, a punctuation mark or another typographic mark.
The Ancient Greek word χαρακτήρ ('charaktēr') is an agent noun of the verb χαράσσω (charassō) with a meaning "to sharpen, to whet", and also "to make cake", from a PIE root "cut" also continued in Irish gearr and English gash, which is perhaps an early loan ultimately from the same Greek root.
A χαρακτήρ is thus an "engraver", originally in the sense of a craftsman, but then also used for a tool used for engraving, and for a stamp for minting coins. From the stamp, the meaning was extended to the stamp impression, Plato using the noun in the sense of "engraved mark". In Plutarch, the word could refer to a figure or letter, Lucian uses it of hieroglyphs as opposed to Greek grammata (Herm. 44)
Metaphorically, it could refer to a distinctive mark, Herodotus (1.57) using it of a particular dialect, or (1.116) of a characteristic mark of an individual. The collective noun χαρακτηριστικά "characteristics" appears later, in Dionysius Halicarnassensis.
Via Latin charactēr, Old French caracter, the word passed into Middle English as caracter in the 14th century. Wycliffe (1382) has "To a caracter [...] in her " () for the mark of the beast (translating χάραγμα "imprinted or branded mark").
Grapheme and Glyph
The word "character" was used in the sense of letter or grapheme by William Caxton, referring to the Phoenician alphabet: (Eneydos 6.25). As in Greek, the word was used especially for foreign or mysterious graphemes (such as Chinese, Syriac, or Runic ones) as opposed to the familiar letters; in particular of shorthand (in David Copperfield (chapter 38) sarcastically of shorthand, "a procession of new horrors, called arbitrary characters; the most despotic characters I have ever known"), and since 1949 in computing (see character (computing)).
As a collective noun, the word can refer to writing or printing in general (Shakespeare's sonnet nr.