How do Pie charts operate on more than one data series at a time?

Pie charts typically represent a single data series by displaying the proportion of each category as a slice of the whole. However, to visualize multiple data series, you can use multiple pie charts side by side or stacked, each representing a different series for comparison. Alternatively, a "doughnut chart" can be used, which allows for multiple rings, where each ring represents a different data series, providing a way to compare proportions within the same visual context. This approach maintains clarity while allowing viewers to analyze relationships between the different data sets.