Risk is not visible.
But we want to deal with risk.
"Risk" is a word with various meaning.
Some people use "risk" to ensure their opinions easily.
In this site, there are two meaning, "quantity of risk" and "the situation which occurs the worst scenario".
In the studies of "chemical substances", "machines" and "finance", risk is a keyword. I walked around a book store to look for books of risk. It was an interesting experience.
I classify risks below. But classification is difficult.
Some methods for Risk of Machines Are developed in Reliability Engineering
The upper classified risks have own ideas and methods.
I write common method and ideas below.
Risk is studied in psychology because risk is a
psychological measure.
When we predict worse scenario with
Regression Analysis
or
Simulation
, and when we judge "the condition is bad" with Statistics,
Such analysis are called "risk analysis".
In risk analysis, risk itself is not always a quantity.