The other day a student asked me what the difference between the prefixes "multi-" and "poly-" was, and if they were interchangable. Well I knew they were synonymous (have the same meaning) but they are not intrchangeable and I didn't know why. Well I did some research and it turns out, multi- is derived from Latin & the words to which it is prefixed tend to be from Latin too. (as in multilinguist) poly- is from Greek & the words to which it is prefixed tend to be from Greek (as in polyglot, which is essentially the same as multilinguist). When the words were created, it seems that hybrid Greek-Latin forms were undesirable, though there are some examples like monolinguist (hybrid version) & monoglot (Greek version).