Just for fun, I'm wondering if anyone can give examples of common symbols/variables that are used in completely different ways depending on the context.
Some examples I can think of off the top of my head:
- $| \cdot|$ indicates absolute value and the order of an element
- $I$ indicates the identity matrix and a ring ideal
- $\implies$ means "implies" and convergence in distribution
- $\mathcal{O}$ indicates big-O notation and the orbit of a point
- $e$ indicates the group identity and Euler's number
- $\pi$ indicates circumference/diameter and a projection mapping
- $P$ indicates an invertible matrix and a probability measure
- $\mu_X$ indicates the expected value of $X$ and the law of $X$
- $E$ indicates a metric space and an elementary matrix