rectangle vs parallelogram

rectangle and parallelogram both are nouns.

Word	Noun	Adjective	Verb	Adverb
rectangle	Yes	No	No	No
parallelogram	Yes	No	No	No

As nouns, parallelogram is a hypernym of rectangle; that is, parallelogram is a word with a broader meaning than rectangle:

rectangle: a parallelogram with four right angles
parallelogram: a quadrilateral whose opposite sides are both parallel and equal in length

rectangle (noun)	parallelogram (noun)
a parallelogram with four right angles	a quadrilateral whose opposite sides are both parallel and equal in length