Infections are a cause of encephalopathy. Many types of bacteria, viruses, and fungi can cause encephalitis by infection and inflammation of the brain tissue or of the meninges (meningitis) that line the brain and spinal cord.
A value of zero indicates that there is no relationship between the two variables. If the correlation coefficient of two variables is zero, it signifies that there is no linear relationship between the variables. However, this is only for a linear relationship; it is possible that the variables have a strong curvilinear relationship.
More generally, for a polynomial of an arbitrary degree, the discriminant is zero if and only if it has a multiple root, and, in the case of real coefficients, it is positive if and only if the number of non-real roots is a multiple of 4.