forge/lang/vendor/nova/en/validation.php

<?php

declare(strict_types=1);

return [

    /*
    |--------------------------------------------------------------------------
    | Validation Language Lines
    |--------------------------------------------------------------------------
    |
    | The following language lines contain the default error messages used by
    | the validator class. Some of these rules have multiple versions such
    | as the size rules. Feel free to tweak each of these messages here.
    |
    */

    'attached' => 'This :attribute is already attached.',
    'relatable' => 'This :attribute may not be associated with this resource.',

];