When:
A past action has a result in the present, so it is still noticable.
Past experiences or situations that are still true.
For, Yet, Never, Ever, Just, Already, Since --> FYNE JAS, So far and recently.
How:
- Positive: have/has + the past participle
Regular verbs: verb + ed/d
Irregular verbs: third row of irregular verbs
- Negative: have/has + not + the past participle
- Question: have/has + subject + past participle