:first-child

:only-child

:last-child

:nth-child(A)
div p:nth-child(2) selects the second p in every div

:nth-last-child(A)
:nth-last-child(2) selects all second-to-last child elements.

:first-of-type
span:first-of-type selects the first span in any element.

:nth-of-type(A) // A에 even odd 가능
.example:nth-of-type(odd) selects all odd instances of a the example class.

:nth-of-type(An+B)
span:nth-of-type(6n+2) selects every 6th instance of a span, starting from (and including) the second instance.

:only-of-type
Select elements that are the only ones of their type within of their parent element

:last-of-type
Select the last element of a specific type

:empty
Select elements that don't have children

:not(X)
Select all elements that don't match the negation selector
:not(.big, .medium) selects all elements that do not have class="big" or class="medium"

[attribute]
Select all elements that have a specific attribute

[attribute="something"]

[attribute^="a"]
Start with a

[attribute$="ato"]
End with ato

[attribute*="obb"]
contain obb