Definition:Limit Ordinal

Definition
An ordinal $\lambda$ is a limit ordinal iff it is neither the zero ordinal nor a successor ordinal.

Notation
The class of all nonlimit ordinals is sometimes denoted $K_I$, while the class of all limit ordinals is sometimes denoted $K_{II}$.

Also defined as
Some sources also consider the zero ordinal a limit ordinal.

It's a matter of taste.