Wide angle ----- Fisheye

[Upatdawn]

I have a Nikon d5300 (crop sensor?) which - i understand - means the stated focal length of a lens is increased, what would be a wide angle lens, i have a 18-140mm but assume its not 18mm with the "virtual" increase from me having a 3/4 sensor? and when does a wide angle go "fisheye", lower than....what mm?

ta

[Upatdawn]

I guess my real question was when do I get fisheye images on a crop sensor camera, at what actuall lens focal length, 18mm = not (i know) what about (say) 12mm? lower?