How to remove error jQuery(...).validate is not a function?

There is a feedback form with a file upload.
Have been using the validator field.
But now it is not needed, so removed.

And now the form simply reloads the page.
The console writes error:
Uncaught TypeError: jQuery(...).validate is not a function at HTMLDocument.5bbf255559caa154366297.png
How to remove it?

Thanks to all the answers

 // =validation
 var errorTxt = 'Error sending';
 jQuery("#sendform").validate({ // LINE 17. HERE THE ERROR REFERS
 submitHandler: function(form){
 jQuery("#message-fos").html('<p class="thank">Data sent...<p>');
 var form = document.forms.sendform,
 formData = new FormData(form),
 xhr = new XMLHttpRequest();"POST", "multisend.php");

 xhr.onreadystatechange = function() {
 if (xhr.readyState == 4) {
 if(xhr.status == 200) {
 jQuery("#message-fos").html('<p class="thank2">Data to send!<p>');

If you delete this method, you receive another error. What to do?
March 12th 20 at 08:41
1 answer
March 12th 20 at 08:43
well, if you deleted the plugin then delete this method from a script, with no libraries validate will not work
thanks for the reply.
however, already deleted this line and its closure.
error starts appearing elsewhere. - Jessie_Skile commented on March 12th 20 at 08:46
@Jessie_Skile, remove from another place =) - Christopher commented on March 12th 20 at 08:49
@Christopher, thanks for the advice =) the script still won't work - Jessie_Skile commented on March 12th 20 at 08:52
@Jessie_Skile, we need a method to remove, and not one line to zakommentirovat
b43b437ad2.jpg - Christopher commented on March 12th 20 at 08:55

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