<p>The heart, an organ that beats quickly is vital to living. OR
THe heart, an organ that beats quickly, is vital to living</p>
<p>WHich is correct: the one with one comma or the one with two commas?</p>
<p>The heart, an organ that beats quickly is vital to living. OR
THe heart, an organ that beats quickly, is vital to living</p>
<p>WHich is correct: the one with one comma or the one with two commas?</p>
<p>two commas</p>
<p>the second one. the one w/2 commas, as daria1000 said.</p>
<p>the reasoning behind is this is that if you get rid of "an organ that beats quickly" then the sentance reads" The heart is vital to living." So that is an independent clause. But the fragment-"an organ that beats quickly"-is a dependent clause, so when you put a dependent clause between an independent, you need a comma in the beginning of the dependent clause (right before you start the dependent clause) to set it off, and one in the end of the dependent clause.</p>