The notion of a property is very domain dependent in computer documentation. Some object-oriented systems speak of properties; the components from which GUIs are constructed have properties; and one can speak of properties in very general terms, as in “the properties of a relational database.”

You might use property for any of these in your documentation.

classname, symbol, token, type

<article xmlns='http://docbook.org/ns/docbook'>
<title>Example property</title>

<para>When Emacs is running under X Windows, the <property>borderWidth</property>
resource controls the width of the external border.
</para>

</article>