Error in Browser Inspector

Hi Chandrakesh!
At first many thank´s for this very useful Comments Validation Pluging. For a plugin like this I searched a Long time and it works perfect at my Site 🙂

Now by checking my Website I discovered an Error in the Browsers CodeInspector:

Uncaught TypeError: $(…).validate is not a function

<script>
		jQuery(document).ready(function($) {

			$('#commentform').validate({
				rules: {
					author: {
						required: true,
						minlength: 2
					},

					email: {
						required: true,
						email: true
					},

					url: {
						url: true
					},

					comment: {
						required: true,
						minlength: 20
					}
				},

				messages: {
					author: "Überprüfen Sie bitte das Namensfeld",
					email: "Geben Sie bitte eine gültige Emailadresse ein.",
					url: "Geben Sie bitte eine gültige Webseitenadresse ein.",
					comment: "Die Nachricht muss zumindest 20 Zeichen betragen."
				}
			});
		});
	</script>

Where the Error is marked red in Codeinspector: (‘#commentform’)

To get sure that this error isn´t caused by an other Plugin I tested this on a fresh WordPress 4.3 Installation with different WordPress Themes.

I hope you can help me to resolve this Error. Thn ak´s for your Reply.

With best Regards,
Karl