storage vs retention

storage and retention both are nouns.

Word	Noun	Adjective	Verb	Adverb
storage	Yes	No	No	No
retention	Yes	No	No	No

As nouns, retention is a hypernym of storage; that is, retention is a word with a broader meaning than storage:

Other hypernyms of storage include holding, keeping.

storage (noun)	retention (noun)
the commercial enterprise of storing goods and materials	the act of retaining something
the act of storing something	the power of retaining liquid
depositing in a warehouse	the power of retaining and recalling past experience
a depository for goods
an electronic memory device
(computer science) the process of storing information in a computer memory or on a magnetic tape or disk