Here's why:
* Prefixes are word parts added to the beginning of a word to modify its meaning (e.g., "un-", "pre-", "re-").
* Suffixes are word parts added to the end of a word to modify its meaning or grammatical function (e.g., "-ing", "-ly", "-ness").
"Polyuria" is formed from the Greek words "poly" (meaning "many" or "much") and "ouron" (meaning "urine").