mittelschmerz vs pain sensation

mittelschmerz and pain sensation both are nouns.

Word	Noun	Adjective	Verb	Adverb
mittelschmerz	Yes	No	No	No
pain sensation	Yes	No	No	No

As nouns, pain sensation is a hypernym of mittelschmerz; that is, pain sensation is a word with a broader meaning than mittelschmerz:

mittelschmerz: pain in the area of the ovary that is felt at the time of ovulation (usually midway through the menstrual cycle)
pain sensation: a somatic sensation of acute discomfort

Other hypernyms of mittelschmerz include pain, painful sensation.

mittelschmerz (noun)	pain sensation (noun)
pain in the area of the ovary that is felt at the time of ovulation (usually midway through the menstrual cycle)	a somatic sensation of acute discomfort