boost_1_45_0/libs/program_options/doc/glossary.xml

<?xml version="1.0" standalone="yes"?>
<glossary>
    <title>Glossary</title>

    <glossentry>
        <glossterm>Token</glossterm>
        <glossdef>
            <para>A single whitespace-separated part of
                command line. In other words, an element of <code>argv</code> array.
            </para>
        </glossdef>
    </glossentry>
    
    <glossentry>
        <glossterm>Option</glossterm>
        <glossdef>
            <para>No definition yet. Options typically correspond to
                (name, value) pair. Then can spawn several tokens.
            </para>
        </glossdef>
    </glossentry>

    <glossentry>
        <glossterm>Argument</glossterm>
        <glossdef>
            <para>No definition yet.
            </para>
        </glossdef>
    </glossentry>

    <glossentry>
        <glossterm>Command line element</glossterm>
        <glossdef>
            <para>A complete part of command line. May
                be either option or argument.
            </para>
        </glossdef>
    </glossentry>

    <glossentry>
        <glossterm>Parameter</glossterm>
        <glossdef>
            <para>The syntactic element which specify value of an
                option.
            </para>
        </glossdef>
    </glossentry>
</glossary>