This is the 665th most frequent Portuguese word.
online
Connected to or available through the internet.
In this sentence, 'online' is used as an adverb to describe the action of purchasing the ticket using the internet.
Eu comprei o ingresso para o filme online.
I bought the ticket for the movie online.
Here, 'online' functions as an adjective, modifying 'option' to specify the type of learning available.
Este curso oferece uma opção de aprendizado online.
This course offers an online learning option.
'Online' in this case acts as an adverb, detailing where or how the streaming of the event will occur.