APPROXIMATION
What do you think what is approximation?
Our electronic definitions web site has answer for that as well:



approximation

a way to retain your sanity with semiconductor devices. Exact answers are tedious and time-consuming and almost never justified in the real world of electronics. On the other hand, approximations give us quick answers, usually adequate for the job at hand.


Other electronic terms somewhat related to approximation
ideal diode ideal transistor second approximation third approximation