Emily Dickinson Lexicon

CI'PHER, n. [Fr. chiffre; Arm. chyfr or cyfr; It. cifera or cifra; Sp. and Port. cifra; D. cyffer; G. ziffer; Dan. ciffer; Sw. ziffra; Russ. tsiphir; Ar. صِفْْرٌ siforon, empty, and a cipher.]

1. In arithmetic, an Arabian or Oriental character, of this form 0, which, standing by itself, expresses nothing, but increases or diminishes the value of other figures, according to its position. In whole numbers, when placed at the right hand of a figure, it increases its value ten fold; but in decimal fractions, placed at the left hand of a figure, it diminishes the value of that figure ten fold.
2. A character in general. – Ralegh.
3. An intertexture of letters, as the initials of a name, engraved on a seal, box, plate, coach or tomb; a device; an enigmatical character. Anciently, merchants and tradesmen, not being permitted to bear family arms, bore, in lieu of them, their ciphers, or initials of their names, artfully interwoven about a cross. – Encyc.
4. A secret or disguised manner of writing; certain characters arbitrarily invented and agreed on by two or more persons, to stand for letters or words, and understood only by the persons who invent, or agree to use them. This is a mode of communicating information by letters, in time of war, with a view to conceal facts from an enemy, in case the letters should be intercepted. This art has given rise to another art, that of deciphering; and hence cipher is used for a key to unravel the characters. To have, or to learn a cipher, is to be able to interpret it.