A palindrome is a word, phrase, number or other sequence of units that has the property of reading the same in either direction (the adjustment of punctuation and spaces between words is generally permitted). The word "palindrome" was coined from Greek roots Greek πάλιν (palin) "back" and δρóμος (dromos) "way, direction" by English writer Ben Jonson in the 1600s. Composing literature in palindromes is an example of constrained writing.
Semordnilap is a name coined for a word or phrase that spells a different word or phrase backwards. "Semordnilap" is itself "palindromes" spelled backwards. Semordnilaps are also known as heteropalindromes, semi-palindromes, half-palindromes, reversgrams, mynoretehs, reversible anagrams , word reversals, or anadromes . They have also sometimes been called antigrams , though this term now usually refers to anagrams with opposing meanings.
Some examples include:
- "Straw" becoming "Warts"
- "Ton" becoming "Not"
- "Star" becoming "Rats"
- "God" becoming "Dog"
and vice versa. Words can be made longer by adding an 's' on the end to make it plural (i.e. "Tar" becoming "rat" going to "Star" becoming "Rats" just by adding an 's'), although the reverse word or phrase would have to make sense (or not).