Is there a term for words that when reversed, form other words?

Question

I'm aware of what a palindrome is. What do you call words that, when reversed, form other words, such as ton (not) and part (trap)?

Answer 1

Semordnilap is a common name for them, which has been pretty well accepted.

I know that Carroll used them in his work, but I think the term (read it backwards) was invented later.

Answer 2

Wikipedia's Palindrome article gives semordnilap, as Mark Wallace's answer correctly pointed out. It also lists several alternatives:

volvograms, heteropalindromes, semi-palindromes, half-palindromes, reversgrams, mynoretehs, reversible anagrams, word reversals, or anadromes.

Such pairs could also reasonably be called mutual palindromes, by analogy with mutual recursion and mutual quine

Answer 3

It is a type of anagram:

An anagram is a type of word play, the result of rearranging the letters of a word or phrase to produce a new word or phrase, using all the original letters exactly once; e.g., orchestra = carthorse,

Any word or phrase that exactly reproduces the letters in another order is an anagram.

Nota Bene: The emphasis is mine.

Answer 4

It is an Anadrome.

An anadrome is a word that has its spelling derived by reversing the spelling of another word. It is therefore a special type of anagram. There is a long history of names being coined as ananyms of existing words or names for entities related to the thing named by this subset of anadromes.

https://en.wikipedia.org/wiki/Anadrome

Answer 5

The word levidrome was created by a six-year-old Canadian boy, called Levi Budd, who realized that there wasn't a term for a word which when read backwards spelled a different word. For example, spits and tips, stop and pots, stressed and desserts

The word levidrome is a blend of the boy's first name and palindrome, a word or phrase that runs the same backwards and forwards, such as “race car”.

William Shatner sent a tweet to the editors of Oxford Dictionaries extolling the virtues of this newly coined word. At 9:39 AM - 8 Nov 2017 the editors replied:

Thank you very much for your email to Oxford Dictionaries. We are always grateful to receive contributions and feedback, but because of the quantity of correspondence, we are not in general able to reply personally to specific content comments or language queries. All submissions are passed on to our editorial team, who will take your comments into consideration when updating the dictionary data.
Kind regards, The Oxford Dictionaries team

An editor at Oxford Dictionaries made a YouTube video dedicated to Levi, which was posted on their blog November 24, 2017

So, the neologism has not yet entered the Oxford English Dictionary but its editors are keeping a close watch. In the meantime, levidrome has its own hashtag on twitter.

Thanks to social media and because Levi Budd is still a child the term levidrome stands a reasonable chance of sticking than the unpronounceable, and virtually meaningless, semordnilap. We may remember how to write it (it's palindrome backwards) but it's highly unlikely that we would ever say it in everyday life.

Levidrome slides into everyday lexicon Mar. 31, 2018