Crop factor
Cropfactor · Lens & optics
The multiplier showing how much a smaller sensor crops the image compared to full frame.
An APS-C sensor (Nikon/Sony/Fuji) has a crop factor of 1.5. Canon APS-C is 1.6. Micro Four Thirds is 2. A 50mm lens on APS-C behaves like a 75mm on full frame. This has advantages (more reach for wildlife) and disadvantages (wide angle becomes less wide).
Tools that help with this: