Used to mark text that should appear lower than the baseline and slightly smaller; inferior or subscript text.


Content Model

<!ELEMENT  sub          (#PCDATA %emphasized-text;)*                 >

Expanded Content Model

(#PCDATA | email | ext-link | uri | inline-supplementary-material | related-article | related-object | bold | fixed-case | italic | monospace | overline | roman | sans-serif | sc | strike | underline | ruby | alternatives | inline-graphic | private-char | chem-struct | inline-formula | tex-math | mml:math | abbrev | milestone-end | milestone-start | named-content | styled-content | fn | target | xref | sub | sup)*


This element may be contained in:

Example 1

Ordinary subscripts:
<fig id="f7" orientation="portrait" position="float">
<label>FIG. 7.</label>
<p>(2Si=O-H)<sup>+</sup> complex formation mechanism via three-fold 
coordination of the O atom with subsequent H 1<italic>s</italic> level 
lowering and extra electron donation to a DB in SiO<sub>2</sub> and to 
the Si conduction band in the SiO<sub>2</sub>/Si interface, respectively.
Electron excitation over to the SiO<sub>2</sub> conduction band denoted 
by a symbol × is not allowed because the energy needed for excitation over 
to SiO<sub>2</sub> conduction band is larger than the H 1<italic>s</italic> 
level lowering.</p>
<graphic orientation="portrait" position="float" xlink:href="f7"/>
<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>

Example 2

As shown formatted above, a subscript and superscript in a “stacked” arrangement:
<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>