>May I think that symbols exist in Ruby becuase Ruby's strings are not
>immutable?
>Python, Java, and C# don't have symbols as far as I know.
>Is it because their strings are immutable?

Java has an equivalent, actually. Interned Strings (http://mindprod.com/jgloss/interned.html). They're odd, in that they have the same class as normal Strings, but they satisfy the qualities other people are talking about -- object equality for equal strings, for instance.

Dunno about Python & C#.

Devin