Why is self-induced $emf$ known as back $emf$?

(N/A) Self-induced $emf$ is produced in a coil whenever the current flowing through it changes,as described by Faraday's Law of Induction. According to Lenz's Law,the direction of this induced $emf$ is always such that it opposes the change in magnetic flux that produced it. When the current in the circuit increases,the self-induced $emf$ acts in a direction opposite to the applied voltage,thereby opposing the growth of the current. Similarly,when the current decreases,it acts to oppose the decay of the current. Because it acts in opposition to the source $emf$ or the change in current,it is commonly referred to as back $emf$.