an audible acoustic wave frequency
"The audio engineer adjusted the equalizer to amplify the low-frequency audio waves that were barely audible in the recording."
a recording of acoustic signals
"I couldn't hear your voice clearly on the audio because there was too much background noise from the construction site outside."
the sound elements of television
"The technician adjusted the audio levels to ensure the dialogue on the new TV program was clear and balanced."
A sound, or a sound signal
"The audio from the damaged speaker crackled loudly before it cut out completely."
In plain English: Audio is sound that you can hear, like music or voices coming from speakers or headphones.
"The audio from the broken speaker was so distorted that we could hardly understand the music."
Usage: Use "audio" as a noun to refer specifically to recorded sound or audio signals, such as in an audio file or audio track. Avoid using it as a synonym for general noise or speech unless you are explicitly discussing the technical medium of the recording.
Focused on audible sound, as opposed to sight.
"The museum offered an audio tour that allowed visitors to hear the history of each exhibit without needing a guide."
In plain English: Audio refers to anything related to sound that you can hear.
"The new headphones have excellent audio quality."
Usage: Use audio as an adjective to describe technology or media that deals specifically with sound rather than visual images. For example, say you are listening to audio files instead of watching video clips.
The word "audio" is a clipping of the longer form audio-. It comes from Latin, where it originally meant "hearing." The term traveled into English as part of technical vocabulary related to sound recording and reproduction.