on the top of something—
1. in the highest part of smth.:
- A picnic party had been formed to take tea on the top of the hill.
2. resting on smth.:
- The lightning was attracted by the acorn on the top of the chapel.
3. in the most important place:
- He was on the top of the list of visitors permitted entrance to the Kremlin.
Note: The expression does not fully correlate in meaning with the phrase at the top of something—
1. = on the top of something 1:
- Go straight ahead up the hill and the Botanic Garden is on the left at the top of the hill.
2. = on the top of something 3:
- They are also at the top of the list of people the new Rwandan government wants to execute.
3. (of a street, garden, etc.) at the end that is furthest away from the speaker:
- The new building is at the top of Victoria Street.
on top of something—
1. = on the top of something 1:
- It was incredibly weird to be standing on top of the world’s largest ocean liner in the middle of the Atlantic Ocean.
2. = on the top of something 2:
- The new method provides a platform on top of the satellite that is not spinning.
3. = on the top of something 3:
- To make sure that the Protestant religion stays on top of the league in Northern Ireland, is what the Orange Order is all about.
4. in addition to smth., especially an unpleasant situation or event:
- He borrowed $50 from me and then, on top of that, asked me if he could borrow my car too.
5. knowing all about the latest technology, market trends, etc.:
- Make sure you stay on top of the latest developments and news.