My teacher said oscilloscope cant measure negative voltage so im confused

While it's certainly possible that your teacher is clueless, I suspect that an examination of the context of that remark might make quite a difference. Many scopes have measurement utilities that display things like peak and peak-to-peak values at the press of a button (or three). I would imagine that such measurement utilities will always display a positive value for these measurements and that might be what they were referring to.

 

Hello,

The following PDF will explain a lot about the oscilloscope:

XYZofOscilloscopes.pdf

Bertus

 

Hello,

The following PDF will explain a lot about the oscilloscope:
Bertus

That link appears to confirm the definitions posted so far.
Max.

 

About the teacher, you could have misunderstood the teacher incorrectly.

 

About the teacher, you could have misunderstood the teacher incorrectly.

Which means he understood the teacher.