One of the easier-to-keep resolutions I recently made was to try to be more careful when using the many technical words that populate our discussions. We use the same words for different things, and different words for the same things: think, for example, of words such as driver, buffer, and switch. The result ranges from occasional confusion, even among our technical peers, to serious misunderstanding and design problems.
The word-pair that can really cloud our thinking is "ground" and "common", and the use of the former when we really should use the latter. Ground implies that the circuit and system somehow, somewhere, has an eventual connection to a true Earth ground, with all the technical good and bad that such a connection brings. But so many products these days have no true Earth connection--and I am not referring just to spacecraft. Battery-powered units generally have no need or provision for a true ground connection, and will never see one. Their charging modules, if they have one, may have a true ground on the AC-line side, but may not.
Of course, there are AC-line powered devices which are--in all or part--isolated from Earth ground, for performance or safety reasons, and there are those which must be connected to Earth ground for the same reasons. Having an isolated product, subsystem, or circuit (often called "floating") may be a necessity for some situations, but it means you have to be careful when probing or debugging, since the wrong test set-up can defeat the isolation, adversely affect performance, yield confusing results, or impact the tester safety (equipment and personnel).
So I am trying to be more precise, and use the word "common" when I mean a common-connection point or plane, and "ground" when I mean a point in the circuit which connect to Earth. I'll also try to use the correct schematic symbols for each, as well.
Remember: many commons are not grounds, but most grounds are common!