What do the letters 'A4' mean in the Audi A4 model?

I often see the letters 'A4' in the Audi car model, but I don't know what it stands for or its significance. Can someone enlighten me?

The 'A' in Audi A4 stands for 'Auto Union', one of the original companies that merged to form the modern Audi company in 1932. The '4' represents the fourth generation of the Audi 80/A4 models.

The 'A4' designation means this model sits in the mid-size luxury sedan segment, between the smaller A3 and larger A6 models.

In German, 'A4' is pronounced 'ahd-veer', which translates to 'adventure'. This could explain the model's reputation for sporty driving and advanced technology.