/ul>
</li>
<li><p>**measure ** = nonnegative real function from a delta-ring F such that <span class="math notranslate nohighlight">\(m(\empty) = 0\)</span> and <span class="math notranslate nohighlight">\(m(A) = \sum_n m(A_n)\)</span></p></li>
<li><p><strong>Hilbert space</strong> H: a vectors space with an innor product <span class="math notranslate nohighlight">\(&lt;f, g&gt;\)</span> such that the following norm turns H into a complete metric space: <span class="math notranslate nohighlight">\(|f| = \sq