noun-modifying (irregular)
Used before another noun or inside compounds to give the sense of 'imperial.' In ordinary explanatory Japanese, 帝国の, 皇帝の, or 皇室の may be clearer depending on context.
新婚旅行でインペリアルスイートに泊まった。
We stayed in an imperial suite on our honeymoon.
I stayed at the Imperial Hotel.