Learner's definition of PRECEDENT
1 : a similar action or event that happened at an earlier time
2 : something done or said that can be used as an example or rule to be followed in the future
The judge's ruling was based on a precedent established by an earlier decision.
He says that the government will set/establish a dangerous precedent if it refuses to allow the protesters to hold a rally.
3 [noncount] : the usual or traditional way of doing something