The one rule: every letter, exactly once
Take LISTEN → SILENT. Both words hold the same six letters, E, I, L, N, S and T, one of each. Nothing is left over and nothing is borrowed, so they are anagrams of each other. The order changes; the letters themselves do not.
Repeated letters count separately. POOL has two Os, so any anagram of it needs two Os as well: LOOP → POLO works, but PLOT does not, because it swaps an O for a T. This is where most near-misses fail. Two words can look alike and share nearly every letter, and a single extra or missing tile still rules them out.
The rule also works in the other direction. If a phrase uses every letter of the original and then adds one more, it is not an anagram, however clever it sounds. A spare letter is as fatal as a missing one.
listensilentenlisttinselinlets
teammeatmatetame
Words, phrases and what gets ignored
Anagrams are not limited to single words. DORMITORY → DIRTY ROOM turns one word into two, and ASTRONOMER → MOON STARER does the same. When phrases are involved, the usual convention is to ignore spaces, punctuation and capital letters, and compare only the letters themselves. That is why A DECIMAL POINT → I'M A DOT IN PLACE is accepted even though the apostrophe appears on one side only.
A word is not normally counted as an anagram of itself. Rearranging LISTEN into LISTEN changes nothing, so it does not qualify. A word spelled backwards is a special case of an anagram: STRESSED → DESSERTS and DRAWER → REWARD are both reversals, and both use exactly the same letters.
Where the word comes from
The word comes from Greek, through Latin and French: ana- means "back" or "again", and gramma means "letter". An anagram is, quite literally, the letters written again. The term was in use in English by the late 1500s, when turning a patron's name into a flattering phrase was a fashionable compliment.
How to check one yourself
The quickest reliable test is to sort the letters of both words into alphabetical order. LISTEN sorts to EILNST, and so does SILENT. If the two sorted strings match exactly, the words are anagrams; if they differ by even one letter, they are not.
For longer phrases, count instead. Write down how many times each letter appears on one side, then cross them off as you find them on the other. Anything left at the end, on either side, is the reason the claim fails. The checker at the top of this page does exactly this, one tile at a time, so you can watch the letters pair off.
Why anagrams are worth knowing
Word games are built on them. A Scrabble rack is a set of letters looking for its anagram, and a player who can see that RETAINS also spells STAINER and NASTIER has more places to put a seven-letter word. Cryptic crosswords use them constantly, signalled by words such as "broken", "mixed" or "wild" in the clue.
Writers have used them to hide names. Vladimir Nabokov turned his own name into VIVIAN DARKBLOOM, a minor character in Lolita. In the classroom, unscrambling words is a simple way to practise spelling, because a pupil has to picture the finished word before they can find it.
Questions
- Is a word an anagram of itself?
- Not by the usual definition. An anagram has to be a different arrangement, so rewriting the same word does not count.
- Do spaces and punctuation matter?
- Normally no. Only the letters are compared, which is what lets a single word become a phrase.
- Does an anagram have to be a real word?
- In word games, yes. In puzzles and wordplay the result is usually a real word or phrase too; a random jumble of letters is just a scramble.