Translation guide
In Japanese, the most common way to refer to an air conditioner is エアコン, a loanword from English. There are also native terms like 冷房 (cooling) and 暖房 (heating), but these refer to the function rather than the device itself. For the machine, エアコン is the standard everyday word.
Referring to the machine that cools or heats a room
The most common and natural word for an air conditioner in Japanese. It's a loanword from English and is used in everyday conversation.
エアコンをつけてください。
Please turn on the air conditioner.
この部屋にはエアコンがありません。
This room doesn't have an air conditioner.
Originally referred only to cooling devices, but now often used interchangeably with エアコン, especially in casual speech. Some people still use it specifically for cooling-only units.
クーラーが効きすぎて寒い。
The air conditioner is too cold.
The full loanword, but rarely used in conversation. It sounds formal or technical.
エアコンディショナーの修理を依頼した。
I requested repair of the air conditioner.
Referring to the cooling mode or the act of cooling a room
Means 'cooling' or 'air conditioning' as a function. Often used on remote controls or in settings. Not used to refer to the machine itself.
冷房を入れてください。
Please turn on the cooling.
冷房の設定温度は26度です。
The cooling is set to 26 degrees.
Referring to the heating mode of an air conditioner (heat pump)
Means 'heating'. Used for the heating function of an air conditioner or any heating system. Not the device itself.
暖房をつけてもいいですか？
Can I turn on the heating?
エアコン is the standard modern term for any air conditioner (cooling and heating). クーラー originally meant a cooling-only unit, but many Japanese people now use it casually for any air conditioner. However, in formal contexts or when specifying a device that also heats, エアコン is safer.
新しいエアコンは暖房もできます。
The new air conditioner can also heat.
冷房 means 'cooling' as a function, not the machine. Saying 冷房が壊れた (the cooling is broken) is fine, but 冷房を買う (buy a cooling) is unnatural. Use エアコンを買う instead.