Writers are so used to using the word where in a general sense that I imagine many don’t stop to think just what they are really saying. I’m speaking specifically in sentences like these:
- The Bible contains many verses where people can find hope.
- I heard a lecture where the instructor quoted Shakespeare excessively.
- I saw a movie where the bad guy fell out of a plane.
The word where pertains to a physical location, and none of the subjects in the above sentences are locations. While a lecture is given at a certain location, the sentence is speaking about the content of the lecture. In sentences like these, it is best to use in which. See how much more accurate these read:
- The Bible contains many verses in which people can find hope.
- I heard a lecture in which the instructor quoted Shakespeare excessively.
- I saw a movie in which the bad guy fell out of a plane.
It might be easier to remember to use where only when referring to a place. For example: “I went to the market, where I ran into Jim.” And, in all other cases, you might want to use the “more formal” (but more correct) which: “I read a book in which is contained all the mysteries of the ancient world.”
I’m all for keeping things simple, so you might reword this last sentence this way: “I read a book that contained all the mysteries . . .” But if you really can’t simplify the sentence without losing the gist of what you are trying to say, be sure to check first to see if you are speaking about a location or not.