The past tense of the verb ‘start’ is ‘started’.
In English, the past tense is used to describe actions that have been completed in the past. The verb ‘start’ is a regular verb, which means that to form the past tense, we simply add ‘-ed’ to the base form of the verb. Therefore, ‘start’ becomes ‘started’.
For example, you might say, ‘I started my project last week.’ This indicates that the action of starting the project took place in the past and is now finished.