Anagram
An anagram is a word or phrase formed by rearranging the letters of another word or phrase, using every one of its letters exactly once and adding none.
The exactness is what separates an anagram from a loose scramble. LISTEN and SILENT are anagrams because both use E, I, L, N, S and T once each. Drop a letter or borrow one and it stops being an anagram. The word itself comes from the Greek ana, meaning back or again, and gramma, meaning letter.
Anagrams show up in puzzles in two quite different jobs. As a puzzle in their own right, you are given the scrambled letters and asked to restore the word — the shorter the word, the faster it falls, because there are fewer arrangements to sift. As a device inside a cryptic crossword clue, an anagram is signalled by an indicator word and supplies the answer letter by letter.
Solvers prize anagrams that comment on their source. ASTRONOMER rearranges to MOON STARER, and THE EYES to THEY SEE. These are called apt or ideal anagrams, and finding one is closer to writing than to solving.
Daily Anagram Puzzle — unscramble each word of a famous quote in turn.