CSS Text defines document white space characters as
spaces (U+0020), tabs (U+0009), and segment breaks.
So I wanted to see the definition of "segment break", but surprisingly the link points to §4. White Space Processing Details. This is not useful, because that section has a big preamble before the definition of "segment break". The link should directly point to https://drafts.csswg.org/css-text-3/#segment-break instead.