 child if needed.</p></li>
</ul>
</li>
</ul>
</li>
<li><p>Compression</p>
<ul>
<li><p>Lossless compression: X = X‚Äô</p></li>
<li><p>Lossy compression: X != X‚Äô</p>
<ul>
<li><p>Information is lost (irreversible)</p></li>
</ul>
</li>
<li><p>Compression ratio: <span class="math notranslate nohighlight">\(\vert X\vert /\vert Y\vert \)</span></p>
<ul>
<li><p>Where <span class="math notranslate nohighlight">\(\vert X\vert \)</span> is the number of bits (i.e., file size) of X</p></li>
</ul>
</li>
</ul>
