This element is one half of a Ruby annotation (<ruby>), and it contains the narrative text in the document, which may be as short as a single character, to which a Ruby Textual Annotation (<rt>) should be applied.
Any combination of:
Text, numbers, or special characters
Linking Elements
<inline-supplementary-material> Inline Supplementary Material Metadata
Related Material Elements
Emphasis Elements
Inline Display Elements
Math Elements
Other Inline Elements
Baseline Change Elements