Gary, You may be missing an important part of the "filter" concept.
The part I think you missed when claiming I would call a resin bed in an ion exchange unit a filter (which I would likely NOT DO by the way unless really pressed) is that filtration in the simplest most direct form is mechanical separation based on size. If the porosity of your filter medium is such that it mostly excludes "lumps" above a certain dimension then it "filters" out those lumps. RO "FILTERS", as you know, have a very fine porosity and can pass H2O) molecules but exclude sufficiently larger molecules and certainly will mechanically separate out most things appreciably larger than water molecules. It is not good practice to use a membrane in that manner and they typically have a prefilter to keep from plugging the membrane with sediment B U T a membrane is a filter and it works principally as a size discriminator not unlike a superfine mesh.
We both know that resin beds and their ion exchange mechanism are NOT based on size discrimination. I suppose you could use a resin bed (charged or not) as a filter but it would take a fairly large chunk of stuff to be filtered out mechanically by the resin beads.
A distiller is CLEARLY NOT A FILTER, at least not in the sense of mechanical separation as discussed above and in previous posts.
In a broader sense you can define a filter as a device that separates entities based on some inherent difference(s) and in that broader sense a still is a filter and using this broader definition an ion exchange system with a resin bed is a filter too. Using this broader definition any device or process that discriminates or separates entities based on their inherent attributes is a filter. This holds in electronics, acoustics, optics, and on and on. Even when not couched solely in "water quality professional" approved terminology, I think most reasonable folks would agree to the use of the more restrictive definition of filtration as a mechanical process based on size.
This leaves us with the question of what to call a canister containing a chemical that reacts with a supply stream of water and chemically alters it. These are sold as "filters."
Gets difficult doesn't it? Common usage does not follow definite clear concise definitions.
By the way, Gary, You don't need to put words in my mouth, I have no deficiency in that area. AND...
Yes a RO filter/membrane can be disposed of so it is disposable if that matters.
Pat
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