Jquery way to use a function?

$('#loader').show(); get("req.php", { plugin:pay_type.value, type:'verify', account:account.value, language:language.value, jek:jek.value, period:period.value }, parse_answer); return true; 

I get the error:

Uncaught ReferenceError: $ is not defined

Please tell me how to fix?

Update

So it seems to have figured it out, but now, look, another error:

Uncaught ReferenceError: pay_type is not defined

Line code:

  get("req.php", { plugin:pay_type.value, type:'verify', account:account.value, language:language.value, jek:jek.value, period:period.value }, parse_answer); return true; } 

plugin:pay_type.value - here gives an error.