>say I name an alias sh and in it I want to use the original sh command.
>How can I do it in bash?

First, use a shell function. Then use something like

sh()
{
        command sh "$@"
}

or

cd()
{
        builtin cd "$@" && echo $PWD
}

If you absolutely must use an alias, you can use the `command' or `builtin' builtins within the alias:

alias sh="command sh"
alias cd="builtin cd"

but if you want to do anything even moderately complex, you should use a shell function.

As a special case, bash checks the first word of an alias to see whether or not it is the same as the alias being expanded, and will not do recursive alias expansion if it is, so you could even do without the `command' and `builtin' in the above aliases.

Chet