Electronic terminology

Concerning the backward u with an r Underwriters Laboratory is not what I am asking about. It’s the backward “u “with an “s”. As in 80/us, or 12,000Hz. Or 10us / div, I am studying for the General exam, learning a lot of stuff I didn’t need in my CB golden screwdriver days. I’m reading a section on oscilloscopes. Thanks if anyone can help.
 
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