<p><strong>Mole Definition: </strong>a chemical <a href="https://www.thoughtco.com/definition-of-mass-604563" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">mass</a> unit, defined to be 6.022 x 10<sup>23</sup><a href="https://www.thoughtco.com/definition-of-molecule-605888" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="2">molecules</a>, <a href="https://www.thoughtco.com/definition-of-atom-and-examples-604373" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="3">atoms</a>, or some other unit. The <a href="https://www.thoughtco.com/definition-of-mass-604563" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="4">mass</a> of a mole is <a href="https://www.thoughtco.com/definition-of-gram-molecular-mass-604515" data-inlink="c0cCtvS675bwu8fsBdNqyA&#61;&#61;" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="5">the gram formula mass</a> of a substance.</p><p><strong>Examples: </strong>1 mole of NH<sub>3</sub> has 6.022 x 10<sup>23</sup><a href="https://www.thoughtco.com/definition-of-molecule-605888" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="6">molecules</a> and weighs about 17 grams. 1 mole of <a href="https://www.thoughtco.com/copper-facts-chemical-and-physical-properties-606521" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="7">copper</a> has 6.022 x 10<sup>23</sup><a href="https://www.thoughtco.com/definition-of-atom-and-examples-604373" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="8">atoms</a> and weighs about 63.54 grams.</p><p><strong><a href="https://www.thoughtco.com/chemistry-terms-starting-with-letter-a-604486" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="9">Return to the Chemistry Glossary Index</a></strong></p>