Selectors

Combinators

.parent .child     /* Descendant Combinator           */
.parent > .child   /* Child Combinator                */
.child + .sibling  /* Adjacent Sibling                */
.child ~ .sibling  /* Subsequent sibling              */
.class1.class2     /* Have both classes               */

Attribute selectors

[role="dialog"]    /* Exact                           */
[class~="box"]     /* Has word                        */
[class|="box"]     /* Exact or prefix (eg, value-)    */
[href$=".doc"]     /* Ends in                         */
[href^="/index"]   /* Begins with                     */
[class*="-is-"]    /* Contains                        */

Pseudo-classes

:target
:disabled
:focus
:active
:nth-child(3)      /* 3rd child                        */
:nth-child(3n+2)   /* 2nd child in groups of 3         */
:nth-child(-n+4)
:nth-last-child(2)
:nth-of-type(2)
:checked
:disabled
:default
:empty

Pseudo-classes variations

:first-of-type
:last-of-type
:nth-of-type(2)
:only-of-type
:first-child
:last-child
:nth-child(2)
:only-child