When do I use sang vs sung?

When do I use sang vs sung?

Sang is the past simple tense of the verb sing. We use past simple for actions that happened at a definite time in the past.

Example: I sang a song at the concert yesterday.

Sung is the past participle of the verb sing. We use the past participle when we form the present perfect and past perfect tense. We use the present perfect for actions that happened at an unstated time in the past.

Example: I have sung a song. ( we do not mention when the action happened.)

We use the past perfect for an action that happened before another action in the past.

Example: I had sung a song before the concert ended.

You can read more about these tenses and do some exercises here