| Form | Example | |
|---|---|---|
| Form | was/were + verb-ing | While I was sleeping, she called. |
| Use | in-progress past action · background · interrupted | It rained while we were walking. |
| while + cont · when + simple | background vs interruption | I was reading when she called. |
| Stative | no continuous: know, love, see | They were playing when it started to rain. |