A number of multiple choice questions which I am working on relate to mathematical symbols which represent probability events…in order to tackle the questions, I need to be clear what is/ is not a valid mathematical symbol…. Are a, b, c, d (see below) valid mathematical symbols which can be used to represent a probability event? I think a, b and c are valid symbols, but am not sure about d - can a single letter be used to represent a probability event? I would appreciate any clarification on these symbols i.e. confirmation they are/ are not valid probability symbols. Thanks in advance.

a) S ∩ R (intersection)

b) S ∪ R (union)

c) ~S (complement)

d) S

NB

S stands for swimming, R stands for running