Definition · Plain-language
Palindrome
A palindrome is a word, phrase, number or sequence that reads the same backwards as forwards, such as level, racecar or "madam".
The step most authors miss
Doing CRediT right? Don’t stop at the statement.
A CRediT statement credits you inside one paper. The recognition CRediT was built for happens when those roles are tied to you, persistently. Sign in with your ORCID — free — and claim your CRediT contributions on casrai.org, the home of the standard. They become a verified, portable part of your identity, not a line that disappears into one PDF.
Free: claim your contributions, then export a journal-ready CRediT statement, schema.org structured data, JATS XML, CSV or BibTeX — and preview your public profile. A membership publishes that profile publicly and verifies the journals you serve.
Reading the same both ways
A palindrome is a sequence of characters that is identical when reversed. The simplest are single words: noon, deed, level, civic, radar and rotor all spell themselves backwards. The word palindrome derives from Greek palin ("again") and dromos ("running"), giving the sense of "running back again". Palindromes are a form of wordplay or recreational linguistics, prized for the constraint they impose: every letter must do double duty. Numbers can be palindromic too — 1881 and 12321 read the same in reverse — as can dates, which is why certain calendar days attract attention as "palindrome dates".
Palindromic phrases and sentences
Beyond single words, whole phrases and sentences can be palindromes when spaces, capital letters and punctuation are set aside. Famous examples include "Madam, I’m Adam", "Never odd or even", and the canal-building boast "A man, a plan, a canal: Panama". Writing a meaningful palindromic sentence is a genuine creative challenge, since the constraint tightens with every word. By convention these phrase palindromes ignore word boundaries and punctuation, judging only the letters; under a stricter test that counted spaces, almost none would qualify. The looser convention is what makes longer palindromes possible.
Palindromes beyond language
The palindrome concept extends past words. In mathematics, a palindromic number reads the same in both directions, and such numbers are studied for their own patterns. In biology, palindromic sequences of DNA — where one strand read in one direction matches its complement read in the other — are biologically important and are recognised by certain enzymes. In computing, checking whether a string is a palindrome is a classic introductory programming exercise. Across all these fields the core idea is identical: a sequence that is unchanged when reversed, a small but elegant kind of symmetry.
Key facts
At a glance
- Definition: a sequence that reads the same backwards as forwards
- Origin: Greek palin (again) + dromos (running)
- Word examples: level, civic, kayak, racecar, rotor, radar
- Phrase example: "A man, a plan, a canal: Panama"
- Convention: phrase palindromes ignore spaces and punctuation
- Also found in: numbers, dates, DNA sequences and programming
Common misconceptions
What people often get wrong
Often heard: A palindrome can only be a single word.
Actually: Palindromes also include phrases, sentences, numbers and dates. "Never odd or even" and "A man, a plan, a canal: Panama" are palindromic phrases when spaces and punctuation are ignored.
Often heard: Palindrome phrases must read the same with spaces included.
Actually: By convention, phrase palindromes ignore spaces, punctuation and capital letters, judging only the letters. Under a stricter test counting spaces, almost no long palindrome would qualify.
Often heard: Palindromes only exist in language.
Actually: The idea extends to mathematics (palindromic numbers), biology (palindromic DNA sequences) and computing (a classic string-checking exercise). The common thread is a sequence unchanged when reversed.
Going deeper
