A character  which, standing by itself, expresses nothing, but when placed at the right hand of a whole number, increases its value tenfold.
- The mathematical symbol (0) denoting absence of quantity; zero.
- An Arabic numeral or figure; a number.
- One having no influence or value; a nonentity.
- A cryptographic system in which units of plain text of regular length, usually letters, are arbitrarily transposed or substituted according to a predetermined code.
- The key to such a system.
- A message written or transmitted in such a system.
- A design combining or interweaving letters or initials; a monogram.
- To solve problems in arithmetic; calculate. See Synonyms at calculate.
- To put in secret writing; encode.
- To solve by means of arithmetic.