How to spell :nth?

Question

css

welovepavel.esy.es/1/

.mc_item_wrap_us:nth(0) {
    content: "";
   
    position: absolute;
    margin: -42px 132px;
    border: 20px solid transparent; border-bottom: 16px solid #353535;
    background-color: yellow;
}

.mc_item_wrap_us:nth(1){
        content: "";
 position: absolute;
    margin: -42px 499px;
    border: 20px solid transparent; border-bottom: 16px solid #353535;
    background-color: red;
}

.mc_item_wrap_us:nth(2){
        content: "";
 position: absolute;
    margin: -42px 315px;
    border: 20px solid transparent; border-bottom: 16px solid #353535;
    background-color: green;
}

should work, but it doesn't.
Why?
Thank you!

Answer 1

Not :nth, but :nth-of-type

Answer 2

jsfiddle.net/soledar10/93z0yup5
jsfiddle.net/soledar10/4ckb8jh7

Answer 3

nth-child(2)

Answer 4

:nth-hild
+ it's possible that you use more pseudo-selectors - after, before

Answer 5

Learn the mathematical part (Dmitry Potapenko ©)
htmlbook.ru/css/nth-of-type