noun, noun, used as a suffix
floor; storey
Refers to a level or storey of a building. Often used as a suffix after a number or descriptor, e.g. 二階 (second floor).
このビルは五階建てです。
This building is five storeys tall.
受付は二階にあります。
The reception desk is on the second floor.
noun
Rare standalone noun for stairs; the reading きざはし is more common for this meaning. Modern Japanese usually uses 階段 (かいだん).
See also: 階 (きざはし)
古い文献では「階」を「きざはし」と読んで階段を指すことがある。
In old texts, 階 can be read as きざはし and refer to stairs.
noun, noun, used as a suffix
Technical term in chronostratigraphy for a stage, a unit of geological time. Not used in everyday conversation.
この化石は白亜紀のアルビアン階のものです。
This fossil is from the Albian stage of the Cretaceous period.
counter
counter for floors
Counter used for storeys or floors of a building. Attaches to numbers: 一階 (first floor), 何階 (which floor?).
このデパートは地下二階から八階まである。
This department store has floors from the second basement to the eighth floor.