A number or expression that is set lower than the baseline and slightly smaller, to act as an inferior or subscript
<!ELEMENT sub (#PCDATA %emphasized-text;)* >
Any combination of:
<addr-line> Address Line; <aff> Affiliation; <article-title> Article Title; <attrib> Attribution; <bold> Bold; <chem-struct> Chemical Structure (Display); <citation> Citation; <collab> Collaborative (Group) Author; <comment> Comment in a Citation; <conf-theme> Conference Theme; <copyright-holder> Copyright Holder; <copyright-statement> Copyright Statement; <def-head> Definition List: Definition Head; <disp-formula> Formula, Display; <ext-link> External Link; <font> Font; <gov> Government Report, Cited; <inline-formula> Formula, Inline; <inline-supplementary-material> Inline Supplementary Material; <institution> Institution Name: in an Address; <italic> Italic; <kwd> Keyword; <label> Label (Of a Statement); <monospace> Monospace Text (Typewriter Text); <named-content> Named Special (Subject) Content; <on-behalf-of> On Behalf of; <overline> Overline; <p> Paragraph; <preformat> Preformatted Text; <product> Product Information; <related-article> Related Article Information; <sc> Small Caps; <series> Series; <source> Source; <std> Standard, Cited; <strike> Strike Through; <sub> Subscript; <subtitle> Article Subtitle; <sup> Superscript; <supplement> Supplement Information; <target> Target of an Internal Link; <td> Table Data Cell (XHTML table model); <term> Definition List: Term; <term-head> Definition List: Term Head; <th> Table Header Cell (XHTML table model); <title> Title; <trans-source> Translated Source; <trans-title> Translated Title; <underline> Underline; <verse-line> Line of a Verse; <xref> X(cross) Reference
As shown formatted above, a subscript and superscript in a “stacked ” arrangement:
...
<body>
<p>The <italic>Escherichia coli argU</italic> gene encodes a minor arginine
tRNA, tRNA<sup arrange="stack">Arg</sup><sub arrange="stack">UCU</sub>,
which corresponds to the rare codon AGA and possibly AGG ....</p>
...
</body>
...
An ordinary subscript:
...
<p>This article by Peter Wilmshurst (10 October 1998, pp 996-9)
used the incorrect abbreviation for inspired partial pressure
of oxygen. The abbreviation should have been Pi<sc>o</sc><sub>2</sub>
not Fi<sc>o</sc><sub>2</sub>.</p>
...
format.ent