messages.optional String (default: "(Optional)")

The text message displayed next to a field label when the items.label.optional option is set to true.

Example - set the clear button message

<form id="myForm"></form>

<script>
    $("#myForm").kendoForm({
        orientation: "horizontal",
        formData: {
            ID: 1,
            Name: "Ivan"
        },
        items: [{
            field: "Name",
            label: {
                text: "Name:",
                optional: true
            }
        }],
        messages: {
            optional: "(Optional field)"
        }
    });
</script>