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.