Not all note follow the convention in here (especially earlier notes), but I will try to follow it more closely in the future.

ObjectNotationExplaination
scalarScalars are represented in lower-case letters
vectorVector (and vector-value functions) are represented in bold letters (there are some exceptions, like gradient is often written as something like )
normalized vector
matrixMatrices are represented as upper-case letters
pointPoints are also represented as upper-case letters. Note that in some notes, points and vectors are not distinguished (and in those cases, points will have vector notation like )

Sets

Set Operations

OperationNotationExplaination
set complementUse overline () rather than ^\complement () or ^\mathsf{c} () in this note
set differenceUse rather than \setminus ()

Numbers

SetsNotationExplaination
natural numbersNatural numbers in this note includes . Using for positive numbers
integers
rationals
reals
complex