Ruby symbols are similar to keyword symbols in Common Lisp. There a keyword symbol is a symbol which evaluates to itself: CL-USER 69 > :a-keyword-symbol

Ruby symbols are similar to keyword symbols in Common Lisp. There a keyword symbol is a symbol which evaluates to itself: CL-USER 69 > :a-keyword-symbol :A-KEYWORD-SYMBOL Keywords with a similar name are identical: CL-USER 70 > (eq :a-keyword-symbol :a-keyword-symbol) T One can't set keyword symbols to another value: CL-USER 71 > (setf :a-keyword-symbol 3) Error: Cannot setq :A-KEYWORD-SYMBOL -- it is a keyword. They have certain features of normal symbols, like a property-list with keyword/value pairs.