Why is there a need to distinguish between a fault, a failure, and an error? surely the use of the umbrella term "defect" simplifies matters?

Ac++an of of pi. in , pi is by : pi = 4 – 4/3 + 4/5 – 4/7 + 4/9 - 4/11 + 4/13 - 4/15 + 4/17 . ., to pi (9 ). , if 5 to pi,be as : pi = 4 - 4/3 + 4/5 - 4/7 + 4/9 = 4 – 1. + 0.8 - 0. + 0. = 3.. atoofbe to pi?