What does cipher mean?
A cipher is a systematic method of disguising a message so that only those who know the secret can read it, typically by substituting or rearranging letters and symbols according to fixed rules. Unlike casual codes built around whole words, ciphers operate at the level of individual characters, which is why breaking one requires analysis rather than a simple lookup table. The word has older senses too: it once meant simply the numeral zero — indeed, both "cipher" and "zero" descend from the same Arabic source — and in older literature it described a person of no consequence, a mere nothing. Today cipher is central to cryptography, appearing everywhere from Caesar's ancient substitution scheme to the encryption protecting modern communications. Its related forms, especially "decipher," keep the word firmly embedded in everyday language about secrets, puzzles, and hidden meaning.
A secret system of writing in which letters or symbols are replaced or rearranged according to a key, so that the message is unintelligible without it.
"The spy transmitted her report in a simple substitution cipher."
This is by far the dominant modern sense, especially in cryptography and puzzle contexts.
The numeral zero; a nought.
"In the old ledger, amounts were written out in full because a stray cipher could ruin the sum."
(Dated) A person of no importance or influence; a nonentity.
"In that court, he was treated as a mere cipher, present but never heard."
To put a message into cipher; to encode. Now usually expressed through the derivatives "encipher" and "decipher".
"The clerk ciphered the dispatch before handing it to the courier."
Standard regular plural. In cryptographic contexts, "ciphers" refers to distinct encryption systems (e.g. classical ciphers); the archaic sense of unimportant people also takes this plural.
"Cryptographers study both ancient ciphers and their modern digital descendants."
The word "cipher" and the word "zero" come from the very same Arabic root — before it meant secret codes, a cipher was simply a nought.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cipher
Cipher entered English in the sixteenth century from Old French "cifre", ultimately from the Arabic "ṣifr", meaning "empty" or "zero" — the same Arabic word that gave rise to "zero" via Italian. When Hindu-Arabic numerals first reached Europe, the symbol for nought seemed mysterious and occult, and the word came to be applied to any puzzling, coded form of writing. The verb form developed alongside the noun, surviving most strongly today through its derivatives "encipher" and "decipher".
Related word forms
How cipher is actually used
The spelling "cypher" is an established British variant, though "cipher" predominates everywhere today. As a verb, "cipher" now survives chiefly in the derived forms "encipher" and "decipher"; the sense meaning an unimportant person is largely historical or literary.
Easily confused with cipher
"Cypher" is simply an accepted British variant spelling of "cipher" — the two words mean exactly the same thing.