Uno is one of those Spanish number games that is played and known around the world by families and friends of different ages. Uno is an ideal way of practicing numbers by bending the rules a bit.

There's no real pattern, you just have to learn them: uno, dos, tres, cuatro, cinco, seis, siete, ocho, nueve, diez, once, doce, trece, catorce, quince. Other than veinte (again), they all have a clear relationship with the related smaller number: cuatro <-> cuarenta, ocho <-> ochenta, etc.