Translation guide
The English word "upstairs" can refer to a location, a direction, or a part of a building. In Japanese, the most common equivalent is 二階 (にかい), but the exact expression depends on context, such as whether you are talking about going upstairs, being upstairs, or the upstairs floor itself.
To say that someone or something is on the upper floor of a building.
Literally 'second floor'. In Japanese houses and many buildings, the upper floor is typically the second floor. Use with location particles like に or で.
The children are upstairs.
I'm sleeping upstairs.
Means 'upper floor' and can be used for buildings with more than two floors. More general than 二階.
I live upstairs.
To express movement to the upper floor.
Referring to the upstairs as a part of a house or building.
When the upper floor is not the second floor, or in buildings with many floors.
Works for any floor above the current one. Use the specific floor number if known (e.g., 三階 for third floor).
There was a fire upstairs.
If you know which floor, it's more natural to say 三階 (3rd floor), 四階 (4th floor), etc.
Please use the upstairs bathroom. (if it's on the 3rd floor)
The word 上階 (じょうかい) exists but is formal and rarely used in daily conversation. Stick to 二階 or 上の階.
In English, 'upstairs' can imply the stairs themselves (e.g., 'run upstairs'). In Japanese, you usually specify the floor destination, not the stairs. To emphasize the action on stairs, use 階段 (かいだん) for stairs.
Is there a bathroom upstairs?
She ran upstairs.