The principles for writing an introduction for a diagram are similar to those used when writing about a process.

1. State what you see
2. Give an overview
3. State the number of labels

Model introduction:

The illustration portrays an electric light bulb for home use; it shows the outer and inner structure of the light bulb, and there are 9 labelled parts to the diagram. The bulb is a standard type and has been designated for home use.