Sentai

In Japanese, is a military unit and may be literally translated as squadron, "task force", "group" or "wing". The terms "regiment" and "flotilla", while sometimes used as translations of "Sentai", are also used to refer to larger formations. Sentai television series are Live-action shows with young heros in spandex fighting monsters with their martial arts.
World War II.
It is a term used during World War II by the military of the Empire of Japan. Imperial Japanese Army (IJA) and Imperial Japanese Navy (IJN) Air Service sentai units were equivalent to a group or wing in other air forces. However, the term had slightly different meanings in the IJA and the IJN. The Japanese navy sentai were squadrons of four ships (battleships and cruisers). Japanese submarines were also grouped in sentai.
Power Rangers.
The Mighty Morphin Power Rangers debuted on television in the US in 1993. They are based on Super Sentai shows from Japan. Here the term means "group fighters". It is a group of five color-coded fighters familiar to young Japanese viewers since the 1975 debut of "Go Renjaa" (five Rangers).