Throughout the novel, there are many instances in which the word “passing” is relevantly used or its definition is alluded to. The main usage of the word is to mean “passing as a white person.” This definition is present as a basis for the novel. In the beginning, Irene worries that she will be found out to be black as she sips tea at a cafe in Chicago and Clare stares at her.
Later, she remembers who Clare is and where she knows her from: she was known rather infamously in their home town for passing as white and riding around with older wealthy white men, who would wine and dine her, spend lavishly on gifts for her, and take her to various parties and social events.
The unfortunate fact is that passing is very much so rooted in ideas of self hatred or struggling for power, or often a combination of both. Clare soon admits that she hates her husband and his racist ideas, and wishes that she could tell him off and be true to her self and her race, but of course she can’t because it would completely blow her cover and ruin her life as it is.
In the more literal sense, “passing” in the novel also sometimes means a passing of time, as in the two years that pass between Clare and Irene meeting in Chicago and Irene receiving Clare’s letter. It’s other meaning in the literal sense is Clare’s death that comes at the end of the novel, when Irene pushes her out of the window in a panicking and jealous rage.