For some reason, I used to think that a 7" version of a song was a 7-minute long version.
Then, I started noticing that most 7" versions I came across were in fact around 3:30 long. Upon further inspection (understand "I googled the question"), I found that 7" version was another expression for the radio edit of a song.
My best guess would be that, back in the day, the vinyls used for radio edits were 7 inches in diameter (or radius?) but I can't find this information anywhere.
Surely, someone knows more about this?
EDIT (for context): I'm seeing this 7" version thing a lot in song titles.