Here I mean the kind of Greek that Newton was familiar with: classical Greek. Anyway, in the periodic table of the elements, the number of protons (i.e. the electric charge) of each element is given along with an atomic weight, usually not a whole number. The reason for the fractional atomic weights is the presence of isotopes, in places the atomic weight is a whole number because there the most stable isotope is listed. So anyway, it seems that these isotopes are so called because they are in the same place in the table, hence one could assume that's what isotope means in Greek: "same place". But I think topos can also mean standing or status. And what about tropos, seen in isotropic? What did the Roman language do with these?
Fractional atomic weights are partly due to isotope mixing. However the isotopes themselves do no have integer weights (except C-12, which is the defining weight).
There is surprisingly little difference between Classical Greek and Modern Greek. A friend of mine lived in Greece in the 1980s. In both high school and university, the classes used books in Classical Greek. The difference is primarily in pronunciation and some simplifications in grammar. Today they have switched to the modern dialect, but still, most educated Greeks can read Plato and Euclid in the original texts without any problem. I assume you mean Latin? Modern science began to take shape about half a millennium ago, when Latin was the language of scholarship in Europe. All papers and textbooks were written in Latin. As new discoveries were made, new compound words were coined, and naturally they were coined in Latin. Latin didn't always have the root words, so they mined the Greek lexicon--just as the Romans themselves did. We have continued this practice. Words like "television" and "automobile" are Greek-Latin hybrids. Tele- and auto- are Greek for "distance" and "self," while vision and mobile are familiar Latin words that we have assimilated into English.
Tropos means direction or way, hence isotropic means the same in all directions. In Latin, "locus" is place and "via" is way (where we get "way" from, I suspect). Not sure about direction. Direction in the sense of course, i.e. direction of travel, is "cursus". None of these seems to come from Greek, but then most of Latin doesn't, so far as I know.
Latin and Greek are both Western Indo-European languages and therefore closely related, but they evolved independently from Proto-Western Indo-European. Neither is an ancestor or descendant of the other. As I noted earlier, the Romans had great respect for Greek civilization, which was founded several centuries earlier than their own. They appreciated the Greek philosophers, scholars and proto-scientists, and borrowed much of their vocabulary for terms that didn't exist in Latin.
