Can I not use "negative" in place of "minus"?
Maybe it's my mathematician bias showing, but I think you can. It's what I'd say. Reported.
Mathematicians may say "negative two degrees" and it wouldn't be wrong, but the vernacular is "minus two degrees".
i did "yesterday, it was less than 2 degrees" why was it wrong?
That would be "moins que deux degrés": here, we're missing the "than" part.
Wouldn't it be « moins de » ?
also, why not : "yesterday, it was below 2 degrees"