Simplify the following text for a Grade 9 native English-speaking person.
Original: NCIS ( also called NCIS : Naval Criminal Investigative Service ) is a drama television series on CBS .
Simplified: NCIS was originally referred to as Navy NCIS during Season 1 ; however , `` Navy '' was later dropped from the title as it was redundant . NCIS was joined in its seventh season by a spin-off series , NCIS : Los Angeles , starring Chris O'Donnell and LL Cool J.