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<underline> Underline

Used to mark text that should appear with a horizontal line beneath it.

Usage/Remarks

The @toggle attribute controls the behavior of this element. When the value of @toggle is set to “no”, the emphasized text remains in the requested style, no matter what the surrounding text does. When the value of @toggle is “yes”, if the surrounding text is set to the same emphasis style, the text within this element will change to another emphasis style, so that the text will always be typographically distinct from its surroundings.
Using the element <italic> as an example, setting the @toggle attribute to “no” would mean that material marked as italics will always be italics, even in an italic context. In contrast, if the @toggle attribute was set to “yes” on the <italic> element, if the formatting context imposes italics (whether due to another <italic> element, a stylesheet, some CSS, or other means), then the italics would be turned off within that context, making the emphasized text emphasized by contrast, but not italic. The <italic> element would still produce italics everywhere else.
Attributes
specific-use
toggle
underline-style

Base Attributes

id
xml:base
Models and Context
May be contained in
<addr-line>, <aff>, <alt-title>, <article-title>, <attrib>, <award-id>, <bold>, <chapter-title>, <chem-struct>, <code>, <collab>, <comment>, <compl>, <compound-kwd-part>, <compound-subject-part>, <copyright-statement>, <data-title>, <def-head>, <disp-formula>, <element-citation>, <ext-link>, <fixed-case>, <full>, <funding-source>, <gov>, <inline-formula>, <inline-supplementary-material>, <institution>, <intro>, <italic>, <kwd>, <label>, <license-p>, <main>, <meta-value>, <mixed-citation>, <monospace>, <named-content>, <nav-pointer>, <on-behalf-of>, <overline>, <p>, <part-title>, <preformat>, <price>, <publisher-loc>, <rb>, <related-article>, <related-object>, <related-term>, <role>, <roman>, <sans-serif>, <sc>, <see>, <see-also>, <see-also-entry>, <see-entry>, <series>, <sig>, <sig-block>, <source>, <std>, <strike>, <styled-content>, <sub>, <subject>, <subtitle>, <sup>, <supplement>, <target>, <tbx:crossReference>, <tbx:definition>, <tbx:entailedTerm>, <tbx:example>, <tbx:externalCrossReference>, <tbx:note>, <tbx:pronunciation>, <tbx:see>, <tbx:source>, <tbx:term>, <tbx:usageNote>, <td>, <term>, <term-head>, <term-source>, <textual-form>, <th>, <title>, <trans-source>, <trans-subtitle>, <trans-title>, <underline>, <verse-line>, <xref>
Description
Any combination of:
Content Model
<!ELEMENT  underline    (#PCDATA %emphasized-text;)*                 >
Expanded Content Model

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

Tagged Samples
Underlined text in a paragraph 
...
<p specific-use="indent"><underline>Level 1</underline>: 
This level generally corresponds to the set of common 
letters of the alphabets for that script, if the script 
is alphabetic, and to the set of common characters of 
the script if the script is ideographic or syllabic.</p>
...
Structural underline 
...
<p>... any nonempty bare interval; or <underline>empty</underline> ...</p>
...