“Char cannot be dereferenced” error

I’m trying to use the char method isLetter(), which is supposed to return boolean value corresponding to whether the character is a letter. But when I call the method, I get an error stating that “char cannot be dereferenced.” I don’t know what it means to dereference a char or how to fix the error. the statement in question is:

if (ch.isLetter()) 
{
....
....
}

Any help? What does it mean to dereference a char and how do I avoid doing so?