Both tenses talk about the past, but they connect to the present in different ways. The choice depends on whether the time is finished and whether the result still matters now.
Use the past simple for an action that happened at a specific, completed moment. The time is stated or clearly understood.
Typical time words: yesterday, last week, in 2020, two days ago, when, at 5 o'clock.
Form it with have/has + past participle. Use it when the time is not specified, when the period is unfinished, or when the result is still relevant.
Typical time words: ever, never, already, yet, just, so far, this week, today.
With the present perfect, these two words show how long something has continued.
| Word | Meaning | Example |
|---|---|---|
| since | the starting point | since 2018, since Monday, since I was a child |
| for | the length of time | for two years, for a long time, for ten minutes |
Example: "I have worked here since 2021" and "I have worked here for four years" describe the same situation.
A useful check: if you can add a finished time word such as "yesterday" or "in 2015", you need the past simple.