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