episcleral veins vs venule

episcleral veins and venule both are nouns.

Word	Noun	Adjective	Verb	Adverb
episcleral veins	Yes	No	No	No
venule	Yes	No	No	No

As nouns, venule is a hypernym of episcleral veins; that is, venule is a word with a broader meaning than episcleral veins:

episcleral veins: small veins in the sclera near the corneal margin; empty into the anterior ciliary veins
venule: a minute vein continuous with a capillary

Other hypernyms of episcleral veins include capillary vein, venula.

episcleral veins (noun)	venule (noun)
small veins in the sclera near the corneal margin; empty into the anterior ciliary veins	a minute vein continuous with a capillary