Many counting problems start with the assumption that we have a certain number of men and women or a certain number of couples, with the assumption (often unstated) being that that gender is binary (only men or women) and couples are only heterosexual. (See for example this or this problem or think for example of Hall's Marriage Lemma.) Can anyone suggest a good replacement for the concept of couples in these sorts of math problems that better reflects the societal norms of the latest generation of students?
As an example, I'll routinely replace "men and women" with "undergrads" and "grad students" or something similar depending on the class make up. I'm currently racking my brain for two distinct sets of objects S1 and S2, where we might naturally think of pairing objects in S1 to objects in S2, and where there is one most natural pairing (i.e. replacing men and women, where we compare any heterogeneous couple to pairing men and their wives). Anything I've thought of makes for a ridiculously long word problem. Any suggestions appreciated.
Mod note: If you answer the question please answer the question
What's a replacement for "married couples" in combinatorics problems?
Please, do not provided answers that say there is no need to do so. This is beyond the scope of this question.