We can deduce here that the issue that is a major source of friction between Heathcliff and Catherine in Wuthering Heights is: Social Divide.
<h3>What is source?</h3>
Source is known to be the place or situation from which something originate from. Whenever we talk about source of something, we are actually referring to something that produces another thing.
Thus, we see here that major originator of friction as seen above is social divide.
