Basic Guidelines For English Spellings
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1A book or treatise which is introductory or preliminary to another, usually larger, work.
2Medicine
A symptom, sign, or condition that is characteristic or premonitory of the onset of a disease. Compare "prodrome", prodroma .
Early 17th century (in an earlier sense). From classical Latin prodromus forerunner, precursor, in post-classical Latin also book or treatise which is introductory or preliminary to another, preamble, warning symptom from ancient Greek πρόδρομος precursor, use as noun of πρόδρομος (adjective) running before from προ- + δρόμος running.