<ruby>
Phonetic annotations above the text, like Japanese furigana.
<ruby> wraps the base, <rt> carries the reading and <rp> holds fallback parentheses, which only appear in browsers unable to place the annotation above the line.
It is an entire piece of Asian typography that HTML absorbed as a native element, with its own rules for line breaking and alignment.
<ruby>
標本<rp>(</rp><rt>ひょうほん</rt><rp>)</rp>
</ruby>