Definition:Normal Series/Infinite

Definition
A normal series may or may not terminate at either end:
 * $\cdots \stackrel {\phi_{i - 1} } {\longrightarrow} H_{i - 1} \stackrel {\phi_i} {\longrightarrow} H_i \stackrel {\phi_{i + 1} } {\longrightarrow} H_{i + 1} \stackrel {\phi_{i + 2} } {\longrightarrow} \cdots$

Such a series is referred to as an infinite normal series.

The context will determine which end, if either, it terminates.