The sub element indicates that text should appear with subscript highlighting, or placed lower in relationship to the surrounding text. Subscripted text is often a smaller font than the surrounding text. Formatting might vary depending on your output process. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available.
See appendix for information about this element in OASIS document type shells.
+ topic/ph hi-d/sub
<p>The power produced by the electrohydraulic dam was 10<sup>10</sup> more than the older electric plant. The difference was H<sub>2</sub>O.</p>