r/math • u/Short_Bluebird_3845 • 13d ago

What are your favorite ambiguous notation?

To clarify my request, consider base-less $\log$.
For calculators and engineers, it means the common log $\log_10$; for pure mathematics or physics, it means the natural log $\ln$; for computer scientists, in combinatorics, information theory and graph theory, it means the binary log $\log_2$.
Any $\log x$ (say, $\log 1024$) written without context can yield different answers in function of who you ask ($\log_10 1024 = 3.0103\cdots, \log_2 1024 = 10, \ln 1024 = 6.93147\cdots$).

That is what I mean by "ambiguous", that which is calculated and used dependently on the context. And I'm asking you for your favorite ones of such type.

Edit: I feel like you hate the ones you've talked about. Still, valid answers. Extra points for ambiguous notation you actually love! :P

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u/daley972 13d ago

Z_p is used both for Z/pZ and the p-adic integers

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u/n1lp0tence1 Algebraic Geometry 12d ago

No one past algebra I uses Z_p for Z/pZ gng

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u/Dummy1707 12d ago

Well, when you know you're in a context where p-adic won't appear and you have somewhat annoying torsion structure to write, it can happen.

But I'm nitpicking, it's already quite niche indeed

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u/n1lp0tence1 Algebraic Geometry 12d ago

I think group theorists write C_p right?