What is a palindrome?
A palindrome is a word, phrase or number that reads the same backward as forward, such as level, racecar, 1221 or the phrase A man, a plan, a canal: Panama.
The word comes from the Greek palindromos, meaning running back again. Single-word palindromes in English include madam, kayak, refer, radar, civic and noon. When people make palindrome sentences, they usually ignore spaces, punctuation and capital letters.
Famous examples include Was it a car or a cat I saw?, Never odd or even and Madam, in Eden, I'm Adam. Numbers can be palindromes too, such as 12321, and so can dates: February 2, 2020, written 02/02/2020, read the same in both directions in many formats.
Palindromes in nature and history
Palindromes appear in DNA, where certain sequences read the same on both strands in opposite directions, helping enzymes recognize where to cut. One of the oldest known word squares, the Latin Sator Square found in the ruins of Pompeii, reads the same in several directions. Some languages, such as Finnish, have very long single-word palindromes.
Did You Know?
The longest single-word palindrome in the Oxford English Dictionary is tattarrattat, a word James Joyce invented in his novel Ulysses to describe a knock at the door.