Mean time and While

Mean time noun - Astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator.

While and mean time are semantically related. In some cases you can use "While" instead a noun phrase "Mean time".

While noun - An indefinite but usually short period of time.

Mean time and while are semantically related. Sometimes you can replace phrase "Mean time" with "While", this terms are similar.