The words where and when are often confused in the English language and can seem almost interchangeable.
For example:
- A bridge can be built only when waters meet
- A bridge can be built only where waters meet
- There are moments when I think grammar is too complicated
- There are moments where I think grammar is too complicated
However, in formal writing (and on SAT questions) there is a distinction between where and when and it would be an error to use the wrong word.
The basic rule is that:
- Where should be used when the subject is clearly place related ("I don't know where I put it.")
- In our original sentence about the bridge, "where" is correct, because water meets at a specific location as opposed to a point in time.
- When should be used when the subject is clearly time related ("I don't know when I lost it.")
- In our original sentence about the bridge, "when" is not technically correct, since water doesn't meet at a specific point in time- it meets continuously.
- It would, however, be correct to say "Add the water to the pot when the pot is hot." since that sentence refers to a specific time when water should go into the pot.
