Palindromes and Semordnilaps

Palindrome (noun) - a word or phrase that reads the same backward as forward.

I learned what a palindrome was in October 1969. That was when I met Jane Drakard – now Bradly – whose palidromic surname was the first palindrome I had come across.

The longest palindromic word in the Oxford English Dictionary is the onomatopoeic tattarrattat, coined by James Joyce in Ulysses (1922) for a knock on the door. The Finnish word saippuakivikauppias (soap-stone vendor) is claimed to be the world's longest palindromic word in everyday use.

One of the most famous palindromes is Leigh Mercer's “A man, a plan, a canal—Panama!” from which it can be seen that in phrases the punctuation does not have to be palindromic.

Palindromes need not be confined to language and can be used for numbers and other forms of sequence. Joseph Haydn's Symphony No.47 in G is nicknamed the Palindrome. The third movement, minuet and trio is a musical palindrome. This piece goes forward twice and backwards twice and arrives back at the same place.

Taking this clever concept a stage further, in 2003 the city of San Diego, California commissioned sculptor Roman DeSalvo and composer Joseph Waters to create a public artwork in the form of a safety railing on the 25th Street overpass at F and 25th Streets. The result, Crab Carillon, is a set of 488 tuned chimes that can be played by pedestrians as they cross the overpass. Each chime is tuned to the note of a melody, composed by Waters. The melody is in the form of a palindrome, to accommodate walking in either direction.

Semordnilap is a name coined comparatively recently for a word or phrase that spells a different word or phrase backwards. "Semordnilap" is itself "palindromes" spelled backwards. Examples include -
stressed / desserts
gateman / nametag
deliver / reviled
lamina / animal