Further to the replies you have already received, you can also say

I play basketball at the weekend. 

I'm on holiday. 

Confused

Which the following sentences is correct??

1. I play basketball in weekends
2. I play basketball on weekends
3. I play basketball in the weekends
4. I play basketball on the weekends
5. I'm in the vacation
6. I'm on the vacation

7. I'm on vacation

Confused

Which the following sentence is correct??

1. I play basketball in weekends
2. I play basketball on weekends
3. I play basketball in the weekends
4. I play basketball on the weekends
5. I'm in the vacation
6. I'm on the vacation

I am on vacation.