css – Open dropdown without being a daughter tag

In the event that this is not the case,

I will explain with the code. Generally we do like this:

.menu-dropdown {display: none; list-style: none;}
.menu: hover .menu-dropdown {display: block;}

Should I do this with the ul (drop-down menu) outside the ul (menu)?

For example:

.menu-dropdown {display: none; list-style: none;}
.menu: hover .menu-dropdown {display: block;}

As you can see, it did not work there, but how to do it?