Sorry to interfere with your discusssion. Im still fairly new to this
group, but since Im studying for a mechanics-exam at the moment, I think I
can answer this one:

"Translation" is derived from Latin and means motion on a straight line.

Assume a body (or a mass) consists of several discreet points, then
translation is the
state of motion where all these points move on straight, parallel lines.

Rotation, on the other hand, is defined as all points moving around a
single fixed point (either belonging to the body itself or any other point in

space) on concentric circles.

Gerhard
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