Insertion loss concepts

The term "insertion loss" has become such a popular one and is applied to so many different concepts that it is becoming unsuitable for precise use. Certain other concepts connected with insertion loss such as attenuation and mismatch loss, are in need of clarification. A logical set of definitions and equations are presented as a suggested approach to more precise terminology. The effect of complex characteristic impedance on these equations is given in an Appendix. Specific suggestions are given for changes in the usage of terms, which if acceptable and adopted would improve the situation.