The notation "CP^n" refers to complex projective space, a fundamental concept in mathematics, particularly in algebraic geometry and topology. It is denoted as CP^n and represents the set of all lines through the origin in C^{n+1}, the complex (n+1)-dimensional space. Each point in CP^n corresponds to a line, making it a compact and complex manifold. Complex projective space can be visualized as a higher-dimensional generalization of the projective plane. For example, CP^1 is equivalent to the Riemann sphere, while CP^2 can be thought of as a complex version of the projective plane. These spaces have rich geometric properties and are essential in various fields, including string theory and quantum mechanics.