As noted in Art. 100 of the 2020 NEC: Fault Current, Available (Available Fault Current). The largest amount of current capable of being delivered at a point on the system during a short-circuit condition.

Informational Note: A short circuit can occur during abnormal conditions such as a fault between circuit conductors or a ground fault. (See Informational Note Figure 100.1 in the NEC.)

Fault current is current outside the usual circuit path and with a magnitude that exceeds the normal circuit current. A fault can be line-to-line, line-to-neutral, or line-to-ground. The new NEC Informational Note, Fig. 100.1, helps explain the differences between “Available Fault Current,” “Short-Circuit Current Rating” (SCCR),” and “Interrupting Rating (AIC).” The available fault current is the largest amount of current available at that point on the circuit. It is important to note that the fault current value is not the same throughout the circuit; it becomes smaller as the impedance is increased between the point of the fault and the source of the power.