What does "oliguria" mean and how does it differ from "anuria"?

Oliguria means abnormally low urine output, typically defined as less than 400 milliliters per day or less than 0.5 milliliters per kilogram per hour in adults. The term combines oligo meaning scanty or few and uria meaning urine condition. Anuria means the near-complete absence of urine output, less than 100 milliliters per day, from a meaning without and uria. Both are signs of serious kidney dysfunction or failure. The opposite condition is polyuria, meaning excessive urine production, from poly meaning many, commonly seen in uncontrolled diabetes and diabetes insipidus.