I was reading an article at
https://code.tutsplus.com/tutorials/the-30-css-selectors-you-must-memorize--net-16048
When you check out the demo at Section 17, you get this selector:
input[type=radio]:checked + label {
color: blue;
}
Section 17 covers the pseudo class selector, but this selector seems like an adjacent selector to me. What would you call it?