tension vs stretching

tension and stretching both are nouns.

Word	Noun	Adjective	Verb	Adverb
tension	Yes	No	No	No
stretching	Yes	No	No	No

As nouns, stretching is a hypernym of tension; that is, stretching is a word with a broader meaning than tension:

tension (noun)	stretching (noun)
the action of stretching something tight	exercise designed to extend the limbs and muscles to their full extent
(physics) a stress that produces an elongation of an elastic physical body	act of expanding by lengthening or widening
feelings of hostility that are not manifest
the physical condition of being stretched or strained
a balance between and interplay of opposing elements or tendencies (especially in art or literature)
(psychology) a state of mental or emotional strain or suspense