Can I use my digital Nikon lens with my film camera?

I recently was gifted an old Nikon m90 film camera. I'm wondering if I can use it with my Nikon DX 18-55mm af-s nikkor lens.

It will mount and you can take a photo, but you will get some vignetting, especially at the 18mm end, because the DX sensor (and more importantly - a DX lens) is a bit too small in diameter for 35mm film.

No and Yes. Your DX lens will cause a large amount of vignetting. It will mount on your camera, but only about 1/2 of the frame will have a picture on it. So yes, you can use it, but you shouldn't. Buy a cheap 28-90 AF or 50 1.8 AF or AF-S and you'll be set.

The lens will mount but since it was made for a digital crop sensor camera, the image projected will not fill the whole film frame leaving you with a tiny picture with large dark fuzzy borders.