noun
Refers to sound in a technical or media context, often as opposed to video. Used in compounds like オーディオ機器 (audio equipment).
このテレビはオーディオ出力端子が付いています。
This TV has an audio output terminal.
noun
Often implies high-quality or enthusiast-grade sound systems. Can refer to the whole setup or individual components.
彼は高級なオーディオをそろえている。
He has a collection of high-end audio equipment.