Seichusen - CenterLine Concept.

Enbusen, Seichusen, and Seichumen
Enbu — performance, Sen — line. Enbusen refers to the performance line of kata. Therefore enbusen refers to the line a karateka follows as a kata is executed.
Sei — draw the most power, Chu — centre, or middle, Sen — line. Seichusen refers to the line that the technique follows as it goes toward the opponent. This, also, is the line that the defender must defend against because the attack is coming through this line. In kumite it is important to remember that your seichusen is an ever- changing center that must be defended and from which technique is executed. In kata as you move along the enbusen you defend and attack through the seichusen.
Seichumen refers to the plane that connects your opponent's seichusen with your seichusen.

The image shows several lines and dots: Squeeze Seichusen through Seichumen as much as possible to achieve maximum effect. As you start to understand, it's not just dividing your body in a left and right hand side... Here's what Seichusen means and how it applies to your opponents position.
Therefore your seichusen is an evolving center that must be defended As you move along the enbusen you defend and attack through the seichusen.

Centerline is a fundamental concept in Wing Chun, as well as in other martial arts, that emphasizes the importance of controlling the central axis of the body during combat. The centerline is an imaginary vertical line that runs down the middle of the body, from the top of the head to the groin. Controlling this line is crucial for both offensive and defensive maneuvers. Here are the key aspects of Centerline Concept:

In summary, Centerline Concept is about prioritizing the control and protection of the central axis of the body. It serves as a guiding principle for both offensive and defensive strategies, helping practitioners to maximize their efficiency, speed, and effectiveness in combat.
Related Article: Wing Chun: The Efficient and Practical Chinese Martial Art