A word spelled the same forward and backward is called a palindrome.
Common English examples include “level,” “radar,” “civic,” “madam,” and “racecar.” The comparison normally ignores capitalization and, in phrases, may ignore spaces and punctuation. That is why “A man, a plan, a canal, Panama” is treated as a phrase palindrome even though its surface formatting differs in reverse.
The word comes from Greek roots meaning roughly “again” and “way” or “direction.” English poet Henry Peacham is credited with introducing the term in 1638. The idea itself is much older: the ancient Sator Square, a Latin word square from the first century CE, displays reversible word patterns.
“Palindrome” is broader than a word alone. Numbers, dates, sentences, poems, musical structures and even certain DNA sequences can be described as palindromic when their relevant units reverse symmetrically. A synonym has a similar meaning, a homophone sounds alike, and an anagram rearranges letters; none of those definitions requires forward-and-backward symmetry.