Prepositions:
* On: "The book is on the table." (O livro está sobre a mesa.)
* About: "I want to talk to you about something." (Quero falar sobre algo contigo.)
* Over: "The plane flew over the city." (O avião voou sobre a cidade.)
* Above: "The sun is above the horizon." (O sol está sobre o horizonte.)
* Regarding: "There is information about this topic on the website." (Há informações sobre este tema no site.)
Adverbs:
* Above: "The temperature is above zero degrees." (A temperatura está sobre zero graus.)
Other uses:
* On the subject of: "Let's talk about something else." (Vamos falar sobre outra coisa.)
* Regarding: "I'm writing to you about my order." (Estou escrevendo sobre meu pedido.)
* In addition to: "We have a lot of work to do, on top of that, there is this meeting." (Temos muito trabalho para fazer, sobre isso, tem essa reunião.)
The specific meaning of "sobre" will depend on the sentence and the context in which it is used.