div > ul {
visibility:hidden;
opacity:0;
transition:visibility 0s linear 0.5s,opacity 0.5s linear;
}
div:hover > ul {
visibility:visible;
opacity:1;
transition-delay:0s;
}
/*or*/
.m-fadeOut {
visibility: hidden;
opacity: 0;
transition: visibility 0s linear 300ms, opacity 300ms;
}
.m-fadeIn {
visibility: visible;
opacity: 1;
transition: visibility 0s linear 0s, opacity 300ms;
}