Use the word "top" for the highest point or area of something. Right now, what you are reading is near the top of the page. The words "Learn American English Online" are at the very top of this page.
There’s a lot of snow on top of the mountain.
He’s sitting on top of the balloon.
The tops of these buildings are very colorful and ornate.
He’s wearing a hat on top of his head. It’s called a top hat.
She’s wearing a tank top. (top = shirt)
There are many ways to use the word "top."
He feels like he’s on top of the world. (He’s very happy about something.)
This project is on the top of our list of things to do this week. (It’s very important)
She’s afraid she won’t be able to top her last performance. (When used as a verb, the word "top" sometimes means to beat or to do better.)
What kind of toppings do you want on your pizza? (The word "topping" is a noun. "Toppings" for a pizza are meat or vegetables.)
The waitress topped off his glass with more wine. (She added more wine so that he had a full glass. The past tense of "top" is "topped.")
The news was read at the top of the hour. ("The top of the hour" is when the minute hand on a clock reaches the 12. For example, 3:00 is the top of the hour. When the minute hand next reaches the top of the hour, it will be 4:00.)