When classifying certain martial arts, they usually fall into two very distinctive categories: grappling and striking. Judo and Brazilian Jiu-Jitsu fall into the grappling side of martial arts, and they share a lot of similarities. Even though they are under the same category they are different in a few ways as well. Each sport and the way you are awarded wins defines the differences mainly in the rules of each.
Judo came first in the history of the two and was founded in Japan in the 1800s. It is also officially an Olympic sport, which started in 1964. Competitively there are a few ways to win a match within the rules. The main way to win is to throw your opponent with enough force on his back to gain something called an “Ippon”. An Ippon is a match-winning point that is only awarded when the former move is completed. You may earn other points that don’t result in an instant win, which is when you throw your opponent but he doesn’t land on his back or with enough force. There is also winning by submission from pinning. Patience is key in judo, waiting for your opponent to make a move for you to capitalize on. Judo uses the patience to find leverage on your opponent and uses throws from the standing position.
Brazilian Jiu-Jitsu was formed later in 1909, just like the name implies, in Brazil. BJJ is mainly fought while on the ground. There are strikes and grapples involved but most of the fighting is while you are on your back. There are different ways to win but mainly by scoring points that are awarded by completing different moves on your opponent. You can also win by submission from pins or holds as well. While it is not an Olympic sport, there are plenty of tournaments to take part in across the world.
So in parting, you can see there are a few differences between the two. While BJJ comes from Judo, the key differences come from the style or positions. Judo brings the standing aspect of martial arts while BJJ has the ground portion. This is where the confusion comes from, where the similarities match between them. With the beginning of each match starting from standing positions, but the way the match progresses and win conditions are set to stand different from each other.