A thing or two about Transylvania:
It borders on are near Hungary and it is in Romania. ( the Banat and other smaller provinces border Hungary.) For the most part most people will say it borders Hungary.
It has a population which is mixed between: Romanian, Hungarian, German and other groups. The largest in the last census was Romanian.
What interest me of course is that people have come and gone over time, but the majority of the population is Romanian.
Some consider Transylvania to include the Banat and other regions, but that is hard to argue since each is cultural diverse and unique.