urination vs oliguria

urination and oliguria both are nouns.

Word	Noun	Adjective	Verb	Adverb
urination	Yes	No	No	No
oliguria	Yes	No	No	No

As nouns, oliguria is a hyponym of urination; that is, oliguria is a word with a more specific, narrower meaning than urination:

Other hyponyms of urination include leak, making water, passing water, wetting, lithuresis, nocturia, nycturia, pee, peeing, piss, pissing.

urination (noun)	oliguria (noun)
the discharge of urine	production of an abnormally small amount of urine
	abnormally small production of urine; can be a symptom of kidney disease or obstruction of the urinary tract or edema or an imbalance of fluids and electrolytes in the body