Translation guide
In Japanese, expressing 'horizontal plane' depends on context: geometry, everyday flat surfaces, or technical fields. The most common term is 水平面 (suiheimen) for a level surface, while 平面 (heimen) refers to a flat plane in mathematics or design. For physical horizontality, 水平 (suihei) is often used as a noun or adjective.
A flat, two-dimensional surface extending infinitely in all directions, often in math or physics.
The standard term for a flat plane in geometry, not necessarily horizontal. Use 水平面 for explicitly horizontal.
This figure is drawn on a plane.
Specifically a horizontal plane, often in physics or engineering contexts.
The object is sliding on a horizontal plane.
A physically flat, level surface like a tabletop, floor, or ground.
Common for any level surface, from tabletops to construction.
Please place the cup on the horizontal surface of the table.
Often used as a noun meaning 'horizontal' or 'level', can imply a horizontal plane in context.
Literally 'flat surface', a more colloquial way to describe a horizontal plane.
Please work on a flat surface.
In fields like architecture, surveying, or aviation, referring to a horizontal reference plane.
平面 (heimen) is a general flat plane, not necessarily horizontal. 水平面 (suiheimen) explicitly means a horizontal plane. Use 水平面 when levelness is important.
In casual conversation, 平らな面 (tairana men) or simply 平らなところ (tairana tokoro) is more natural than technical terms.
この板は水平が取れていない。
This board isn't level.
Measure the height from the horizontal datum.