Which feature of a word processing program enables you to represent any numerical data in the form of a diagram?

A chart is a graphical representation of data, in which "the data is represented by symbols, such as bars in a bar chart, lines in a line chart, or slices in a pie chart". A chart can represent tabular numeric data, functions or some kinds of qualitative structure and provides different information.

Including a chart in your document can allow your reader to see the meaning behind the numbers, and it can make showing comparisons and trends easier.

To insert a chart into your document in MS word:

Select the Insert tab, then click the Chart command in the Illustrations group.
A dialog box will appear. Select a category from the left pane, and review the charts that appear in the right pane.
Select the desired chart, then click OK.
A chart and a spreadsheet will appear. The data that appears in the spreadsheet is placeholder source data that you will replace with your own information. The source data is used to create the Word chart.
Enter your data into the worksheet.
If necessary, click and drag the lower-right corner of the blue line to increase or decrease the data range for rows and columns. Only the data enclosed by the blue lines will appear in the chart.
When you're done, click the X to close the spreadsheet.
The chart will be completed.
You can edit the chart data at any time by selecting your chart and clicking the Edit Data command on the Design tab.