1.
on; switched-on state; activated
The 'on' state of a switch, device, or setting, as opposed to オフ ('off'). From English 'on'. Frequently used as オンにする ('to turn on') and in the pair オン/オフ.
Loanword from English 'on', referring to the activated state of a switch, device, or setting. Its opposite is オフ (off).
Common collocations
Usage
Unlike the English preposition 'on', Japanese オン is used only for the switched-on/activated sense. The work-life sense also appears in オンとオフ ('on-duty and off-duty').