Which shape is defined by the equation $\frac{x^{2}}{4}-\frac{y^{2}}{9}$ $=1$ ? Circle Ellipse Parabola Hyperbola None of the above.

Step 1 ：The given equation represents a hyperbola.

Step 2 ：Comparing the given equation with the standard equation, we find that the values of a and b are 2 and 3 respectively.

Step 3 ：Therefore, the shape defined by the equation is a hyperbola.