What is that thing between CSS "selectors" called?

Question

What do you call these:

body > p + p

in a CSS selector? Are they:

• Relational operators
• Position-based criteria
• Something else?

I just have no idea what to call them. Is there an official name?

(And, also, are there official names for a b c in a b c, d e f and a in a b c?)

Answer 1

According to https://www.w3.org/TR/selectors-3/#combinators they are called "combinators".

1. (space character) = descendant combinator
2. > (angle bracket or greater-than sign) = child combinator
3. + (plus mark) = adjacent sibling combinator
4. ~ (tilde) = general sibling combinator

Answer 2

As identified by Tom Haws, the operators between the simple selectors are called combinators. In CSS2 there were only three: +, >, and the space combinator.

• The space is the combinator used in a CSS descendent selector.
• > is the combinator used in a CSS child selector.
• + is the combinator used in a CSS adjacent sibling selector.

In each case, the 'selector' is the full combination of the simple selectors and the combinators.

The range of valid combinators expanded, once CSS Selectors Level 3 was standardized, to include the ~ or "subsequent-sibling" combinator.