Detailed analyses of quantities and units of measure in historical documents may also use the feature structure mechanism described in chapter 19. Feature Structures. The <num> element is intended for use in simple applications.
Example
<p>I reached <num type="cardinal" value="21">twenty-one</num> on
my <num type="ordinal" value="21">twenty-first</num> birthday</p><p>Light travels at <num value="3E10">3×10<hi rend="sup">10</hi></num> cm per second.</p>
