Correlation is a statistical measure that quantifies the relationship between two variables. It is determined as the scaled covariation and due to this scale, we can determine the measure of dependencies in addition to their direction.
Correlation ranges between -1 and 1, where:

1. If the correlation is +1 then values have a perfect positive linear relationship. As one variable increases, the other variable increases proportionally;
2. If the correlation is -1 then values have a perfect negative linear relationship. As one variable increases, the other variable decreases proportionally;
3. If the correlation coefficient is close to 0 then there is no linear relationship between the variables.

To calculate the correlation we can follow the same steps as to calculate covariance and use np.corrcoef(x, y)[0, 1].