revision:
The <rt> tag defines an explanation or pronunciation of characters (for East Asian typography) in a ruby annotation. Use <rt> together with <ruby> and <rp>: the "ruby" element consists of one or more characters that needs an explanation/pronunciation, and an "rt" element that gives that information, and an optional "rp" element that defines what to show for browsers that do not support ruby annotations.
<rt> . . . </rt>
<ruby style="margin-left: 4vw;"> 漢 <rt> ㄏㄢˋ </rt> </ruby>
<ruby style="margin-left: 4vw;"> 漢 <rp>(</rp><rt>Kan</rt><rp>)</rp> 字 <rp>(</rp><rt>ji</rt><rp>)</rp> </ruby>