optional — Optional information.


optional ::=


Common attributes and common linking attributes.

No additional attributes.


The optional element indicates that a specified argument, option, or other text is optional. The precise meaning of optional varies according to the application or process being documented.

Processing expectations

Formatted inline.

Optional arguments in a synopsis are usually given special typographic treatment, and often they are surrounded by square brackets. The optional tag is expected to generate the brackets.

Outside a synopsis, the typographic treatment of optional is application specific.


Common attributes and common linking attributes.

any attribute

Any attribute in any other explicit namespace


These elements contain optional: bridgehead, caption (db.html.caption), citation, citetitle, classsynopsisinfo, computeroutput, contrib, emphasis (db.emphasis), entry, enumitemdescription, firstterm (db.firstterm), funcsynopsisinfo, glosssee, glossseealso, glossterm (db.glossterm), link, literallayout, member, meta (db.meta.content), olink, optional, orgdiv, para, phrase (db.phrase), primary, primaryie, programlisting, quote (db.quote), refdescriptor, refentrytitle, refname, refpurpose, remark, screen, secondary, secondaryie, see, seealso, seealsoie, seeie, seg, segtitle, simpara, subtitle, synopsis, synopsisinfo, td, term, termdef, tertiary, tertiaryie, th, title, titleabbrev, tocentry, userinput.


The following elements occur in optional: text, abbrev, acronym, alt, anchor, annotation, biblioref, coref, date, emphasis (db._emphasis), firstterm (db._firstterm), footnote, footnoteref, foreignphrase (db._foreignphrase), glossterm (db._glossterm), indexterm (db.indexterm.endofrange), indexterm (db.indexterm.singular), indexterm (db.indexterm.startofrange), inlinemediaobject, link, olink, optional, phrase (db._phrase), quote (db._quote), remark, replaceable, subscript, superscript, trademark, wordasword, xref.

See Also

Related elements: computeroutput, constant, literal, markup, option, parameter, prompt, replaceable, tag, userinput, varname.


1 |<article xmlns='http://docbook.org/ns/docbook'>
  |<title>Example optional</title>
5 |ls <option>-abcCdfFgilLmnopqrRstux1</option>
  |   <optional>names</optional>
  |ls -abcCdfFgilLmnopqrRstux1
  |   names