Factually means based on facts rather than opinions, feelings, or guesses. When you state something factually, you're reporting what actually happened or what can be proven true. If your teacher asks what caused the American Revolution and you answer factually, you stick to historical events and documented reasons rather than making things up or sharing personal theories.

When a scientist speaks factually about an experiment, she reports exactly what occurred during her tests. When a news reporter describes an event factually, he tells what happened without adding his own opinions about whether it was good or bad.

You might hear someone say “That's not factually correct” when pointing out an error. If your friend claims that blue whales are the size of school buses, you could respond: “Actually, factually speaking, blue whales are much larger, about the length of three school buses.” The word helps distinguish between what's provably true and what someone merely believes or wishes were true.