or by applying algorithms (when no definitions are provided),
and returns a modified <code>FFTrees</code> object that contains those definitions.</p>
<p>In most use cases, <code>fftrees_define</code> passes a new <code>FFTrees</code> object <code>x</code> either
to <code><a href="fftrees_grow_fan.html">fftrees_grow_fan</a></code> (to create new FFTs by applying algorithms to data) or
to <code><a href="fftrees_wordstofftrees.html">fftrees_wordstofftrees</a></code> (if <code>my.tree</code> is specified).</p>
