Unital

Summary

A unital of order $n$ is a block design with $n^3 + 1$ points and blocks of $n + 1$ points. Any two points lie in exactly one block. The main examples sit inside a projective plane of order $n^2$, where they meet every line in $1$ or $n + 1$ points. The classical example is the Hermitian curve, defined by a Hermitian form over a field with $n^2$ elements.