Something is abstract if it does not exist at any particular place and time, but instances, or members, of it can exist in many different places and/or times (we say that what is abstract can be multiply instantiated). For example, lots of different things have the property of redness: lots of things are red. And we find the relation sitting-on everywhere: many things sit on other things. So the property, redness, and the relation, sitting-on, do not exist in any one particular place. So if we want to say that properties and relations are, or have being, clearly we want to say they have a different sort of being from the sort of being that physical objects, like rocks and trees, have. That accounts for the usefulness of this word 'abstract'. We apply it to properties and relations to mark the fact that if they exist, they do not exist in space or time, but that instances of them can exist in many different places.