A long, thin, and flexible strip used to make things straight or to help them move in a certain way, especially in engineering and design.
The word spline is technical and is often used in math, engineering, and design.
Examples:
The engineer used a spline to make the robot's arm move smoothly.
A spline helps the car's wheels turn the right way.
The spline is long and thin.
The spline is like a long, bendy ruler.
The spline is so long, it can go around the whole building!
The spline helps the bridge stay straight and not fall down.