One of the frustrating things about math is that some symbols are reused again and again, as if someone was afraid of running out of symbols.
For example:
1. ' can mean a derivative of a function, or the transpose of a matrix or vector. This is confusing when a book refers to the derivative of a vector. Hmm, which is it?
2. | | can mean the absolute value of something, or the determinant of a matrix. This is confusing when transforming random variables and you need to refer to the absolute value of a Jacobian determinant.
3. ~ can mean "scales as" or "is distributed as."
4. Σ can mean the operation "sum the following" or the item "covariance matrix."
I'm reminded of Demetri Martin's line about vitamins: "When they were naming vitamins they must have thought there were going to be way more vitamins than there ended up being. OK let's name these: Vitamin A, Vitamin B...ok man slow down we've got a lot to cover here. B2, B3, B4, B5, B6, B12. Then they got to E and they were like 'We're pretty much done. We've got all those damn B's. This is embarrassing. Let's just skip to K and get the hell out of here."
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