- In cryptography, a cipher is a cryptographic system (see cryptography)
in which units of plain text of regular length, usually letters, are
arbitrarily transposed (see transposition
cipher) or substituted (see substitution
cipher) according to a predetermined code, or a message written
or transmitted in such a system. See also Caesar
cipher and Beal ciphers.
- In mathematical nomenclature, a cipher is the symbol (0) for zero.