<p>I am struggling with commas; I can't really comprehend them. I usually think I understand them but see a sentence that throws me off. For example: </p>
<p>London is a very old city with many neighborhoods, some of which are very modern.</p>
<p>Why is the comma usage in this sentence correct?</p>
<p>Usually, you use commas to separate clauses that aren’t required but give more meaning to the sentence. For example,</p>
<p>When I was a child, I would go to the amusement park.
Wing chun, a form of martial arts, is widely practiced in Hong kong.
London is a very old city with many neighborhoods, some of which are very modern.</p>