Source article: sportshealth.com/sportsinjuries/generalinjuries/whatdifferencebetweentendonitistendinosisandtendinopathy

Rotator Cuff Tendonitis would be associated with an acute inflammatory response to overuse or tissue trauma. It often responds positively to rest and recovers in 23 days.

Rotator Cuff Tendinosis is associated with no active inflammation, it is a long term painful condition associated with degenerative tissue and cell changes. It often responds to treatment in 23 months or longer.

Rotator Cuff Tendinopathy is an umbrella term associated with any kind of disease of disorder of the tendon.