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—“My question concerns technical and scientific language rather than colloquial language: I would like to ask if there is any inclination in English to give the words class and category more or less different meanings or shades of meaning, or are they completely interchangeable in all kinds of use?”— From Elsewhere

You CLASSIFY things that exist (Science – referents that exist into a hierarchy) whose organization doesn’t change, and you CATEGORIZE ideas (Philosophy – referents that have meaning into a list) because they can change.

So classify(things, hierarchy or order, relatively invariant), vs. categorize(concepts, terms, that might be categorized differently in different contexts).

So just as english words have origins in german(commoners, farmers, craftsmen), french(nobility, ruling class, wealthy), Latin and Greek(scholarly or educated classes), English (like all european languages) uses specialized vocabulary for mathematical, philosophical, political/Legal, and scientific classes of vocabulary.

English is very ‘precise’ in its use of sets of terms the same way that german is precise in its precisely descriptive terms.

Now, do uneducated people conflate terms? All the time. In fact educated people do all the time as well. My favorite examples being the conflation of mathematic (axiomatic), philosophical(rational), and scientific (theoretic), terminology. It’s not uncommon to hear someone make an argument with terms from math, philosophy, and science without having the faintest idea that the terms in each limit the possible properties of argument. For example, True in math and logic is binary(Deductive and Necessary). In philosophy it can be binary(non contradictory), in law it’s ternary(True false and undecidable), in and in science it’s multivalued with False being the only certainty, and truth being little more than an ordinality by triangulation).

If someone disagrees with you on usage you can correct them. 😉