The highest point the ball reaches during its flight, measured in feet above where it started. It's the payoff of launch angle plus spin working together, and it tells you a lot about how the ball will land. A high apex means a steep descent — the ball stops quickly, which is exactly what you want into greens (tour 7-irons peak near 90 feet, about a 9-story building). A low apex means shallow descent and lots of rollout — fine off the tee, trouble when you need to hold a firm green.