What term describes the number of bits used for each pixel in an image file?

The term that describes the number of bits used for each pixel in an image file is known as colour depth. Colour depth indicates how many different colours can be represented in an image, which directly affects the quality and detail of the image displayed. For instance, a colour depth of 8 bits allows for 256 different colours, while a colour depth of 16 bits can represent 65,536 colours, providing a much richer and more accurate depiction of images.

Pixel depth is a less commonly used term and can sometimes be confused with colour depth, but it generally refers to the same concept. Image resolution refers to the dimensions of the image, usually given in width by height (e.g., 1920x1080), and does not measure the bit depth. A bit map is a specific type of image file format that uses a grid of pixels but does not directly connect to the concept of bits per pixel.