Directly in the insert interface, and then select δ in the formula. Below I will demonstrate the detailed operation steps:

(computer model: MacBook Air, software version: Word 202 1)

1. Open Word and click "Insert" above;

2. Click the formula above;

3. Click on the right triangle above;

4. Click the δ above;

5. The δ typing operation is complete!

The above is a tutorial on how to play δ, I hope it will help you ~