For
- Use “for” to indicate the duration of an action or event.
- It emphasizes the length of time something has been happening or will happen.
- “For” can be used with various time expressions like hours, days, weeks, months, years, etc.
Here are some examples:
- I’ve been working on this project for two weeks. (duration)
- The movie lasted for three hours. (duration)
- We’ll be on vacation for a month. (duration)
Since
- Use “since” to indicate a starting point in the past from which an action or event continues up to the present moment.
- It emphasizes when something began in the past and is still relevant now.
- “Since” can be used with specific points in time like Mondays, Fridays, specific dates, or even non-specific starting points like “a long time” or “childhood”.
Here are some examples:
- I haven’t seen him since Monday. (starting point)
- She’s lived here since 1998. (starting point)
- We’ve been friends since childhood. (non-specific starting point)
Key Difference
Think of “for” as referring to the distance in time (how long), while “since” refers to the starting point in time (when).
Here’s a trick to remember:
- You can use “for” with how long questions. (How long has it been raining?)
- You can use “since” with when questions. (When did it start raining?)
Additionally
- Both “for” and “since” can be used with the present perfect tense to talk about actions that began in the past and continue up to the present.
- “For” can also be used with the simple past tense to talk about completed actions in a definite period of time in the past.
