...you can't say the teacher didn't tell you, at least in this instance. During my world history class in high school, Mr. H. told the class about a person who acted as a de facto king of his country. He wasn't actually the king but made decisions as though he was.
"That made him a de facto king," Mr. H. said. "I'll write that word, de facto, on the board, so the next time you see it in an article, you can say, 'Hey, de facto! I forget what that means.'"
Not every teacher would admit that most students only retain a small fraction of what they learn in class.
