WHY CAN'T I USE Time.deltaTime?!

Until I made a new cs file, added it to a gameObject and then deleted the new file, everything was fine.
Now, I can’t even type Time.deltaTime, because that monodevelop won’t give me the option to write deltaTime after Time, and it also means that every time that I use it, he gives me an error.
I’m building a game, that based on Time.deltaTime, for every step.
There is anyone who knows about this error, or maybe even how to fix it?
Please Help Me!!

Btw I’m using c#

*EDIT - By using “UnityEngine” before Time.deltaTime, it works. but, still I can’t understand why is that happening

I assume the script in question is simply missing the following at the top of the file:

using UnityEngine;

I had the same issue, It was because I had another script with the “Time” class which conflicted with the Global “Time” hence the issue.

Rename your “Time” class (Could be a Time script from a third party plugin too).