How to say "horizontal" in Japanese

Choosing the right word

横よこJLPT N5approx.Common
nounHorizontal as opposed to vertical: sideways orientation or direction, as of an object lying on its side. When the meaning is level or even rather than sideways, 水平 is the better fit.
母親ははおやは赤ん坊あかんぼうをベッドに横よこにした。↗
The mother laid her baby on the bed.
水平すいへいJLPT N2approx.Common
na-adjective, no-adjectiveHorizontal in the sense of level or even: a surface or line that is flat and not tilted. Use it when what matters is being level or even, not sideways orientation.
水みずは水平すいへいになろうとする。↗
Water tries to find its own level.

For 'horizontal' meaning sideways, as opposed to vertical, use 横; for 'horizontal' meaning level or even — a flat, untilted surface — use 水平.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

Japanese equivalents

JLPT vocabulary levels are community estimates, not official (no official lists have been published since the 2010 revision).

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