Prepositions: OVER vs. ABOVE

Native speakers of English usually find it very difficult to explain the difference between the prepositions over and above, but nevertheless have very clear intuitions about when each should be used. Today's post will be getting into some detail about the factors driving these intuitions. The system is quite beautiful in its logic and very revealing about semantic structure.

Prepositions and time: BY vs. UNTIL

[For German speakers]
The German word bis can be translated into English as either by or until, which makes it hard to know which to use. Here is the answer.

Short version
Use by when talking about an event that occurs at a single point in time like finishing.

I will finish the project by Friday

Use until when talking about an activity or state that continues over a period of time like working (an activity) or being asleep (a state).

I will work until 10pm
I was asleep until the phone rang

Prepositions and places: IN, AT, ON

The U.S. president lives in The White House at number 1600 on Pennsylvania Avenue in the city of Washington in the District of Columbia in the United States on Earth. If these are all places, why does English need three different prepositions (in, at and on) to introduce them? Fortunately, the answer follows from general rules about when each of these prepositions should be used.