Marriage in this novel is presented in different ways depending on the different generations of the characters. For both Cathy and Heathcliff, unfortunately marriage is used as a means to an end rather than as a union between two lovers. This is of course something that occurs because of Cathy's feeling that she is unable to marry Heathcliff because he is not socially her equal, even though her love for him is far more eternal and strong than her love could ever be for Linton. Note how she describes her feelings about marriage to Nelly in Chapter 9:
I've no more business to marry Edgar Linton than I have to be in heaven; and if the wicked man in there had not brought Heathcliff so low, I shouldn't have thought of it. It would degrade me to marry Heathcliff, now; so he shall never know how I love him; and that, not because he's handsome, Nelly, but because he's more myself than I am.
Cathy here clearly states that she will not marry Heathcliff because of what it would do to her social standing and also that she does not really love Linton. She later admits that she marries Linton in order to be able to help Heathcliff with her husbands wealth. In the same way, Heathcliff marries Isabella not because he loves her but in order to get back at her husband and gain revenge upon Edgar Linton. Marriage is forced upon the younger Cathy and Linton, and it is only at the end of the novel, in the eventual union of Hareton and Cathy, that marriage becomes a meeting of equals who truly love each other, bringing the generational cycle of bitterness and hatred to a close. Marriage therefore is something that relates to the central themes of the novel that capture the frustrated love and the twisted passions that dominate the characters. Marriage becomes a way to act out those passions.