Taxon is short and sweet. Maybe we should regularise the plural to taxons so that the irregular grammar does not distract from the discussion. This would be consistent with a basic rule of grammar which states that the inflected forms of any word that you have never heard of before are all regular. Some taxa are so easy that we already know them. I think the best one is the birds.
Birds have wings which they use to fly and they have feathers and beaks and two legs.
They lay eggs with hard shells. OK, so some of them don't fly, but we'll deal with that issue later. We see a lot of birds without knowing what particular kind of bird they are, and we just think of them as being birds. So we have to define what a mammal is. The intention of this definition is to name features that are found in all mammals and which clearly distinguish them from those organisms that are not mammals.