# A-level Physics (Advancing Physics)/Current/sigma

That's the Greek letter Sigma. It means 'sum of', so Kirchoff's First Law is stating that the sum of all the currents going into a point equals the sum of all the currents leaving the point. So:

I_{in1} + I_{in2} + I_{in3} + ... + I_{inn-2} + I_{inn-1} + I_{inn} = I_{out1} + I_{out2} + I_{out3} + ... + I_{outn-2} + I_{outn-1} + I_{outn}