未捕获的ReferenceError：在Wordpress中未定义jquery

Can anyone help me out from this issue. I have added a JS to my WordPress site externally. It doesn't produce the output and throws an error in the following code.

Please help me out and get over it.

var clock;

jquery(document).ready(function() {
    var currentDate = new Date();
    // Set some date in the past. In this case, it's always been since Jan 1
    var pastDate  = new Date(currentDate.getFullYear(), - 3, 4, 3);
    // Calculate the difference in seconds between the future and current date
    var diff = currentDate.getTime() / 1000 - pastDate.getTime() / 1000;

    clock = jquery('.clock').FlipClock(diff, {
        clockFace: 'MinuteCounter'
    });
});

JavaScript is case sensitive. Use jQuery instead of jquery:

jQuery(document).ready(function() {
    .
    .
    .

    clock = jQuery('.clock').FlipClock(diff, {
        clockFace: 'MinuteCounter'
    });
});