Bit Depth
Refers to the amount of information that a scanner can read for each pixel scanned. A one-bit scanner can identify only black and white, 24-bit scanners can capture 16.7 million colors per pixel.

DPI/PPI
Dots per inch or Pixels per inch. Refers to the resolution level of a scanner. A scanner reads a document by assigning a number of pixels/dots to the surface of the document. The DPI/PPI refers to the number of pixels that can be read by the scanner in one square inch.

Dynamic Range
Measures the range of tones that a scanner can measure. Similar to bit depth, dynamic range is evaluated from a scale of 0 (absolute white) to 5 (absolute black). Most scanners have a dynamic range between two and three.

Footprint
How much room a scanner takes up on a desk or other flat surface - general indicator of the size of the unit.

OCR
Optical Character Recognition. A type of software which creates editable text from scanned forms, letters, or other written materials. Used primarily for data entry tasks, OCR software transports information to word processing, spreadsheet, or other editing software programs.

Resolution
There are two types of resolution - optical and interpolated. Optical resolution refers to the number of pixels per square inch that a scanner can assign to an image. The more pixels the greater reproduction quality. Interpolated resolution is calculated after the scanner adds theoretical pixels to an image - it averages the colors of two pixels side by side for a third pixel that would theoretically fit in between.

SCSI/USB/Parallel
Refers to the computer ports to which a scanner can be connected. SCSI (pronounced 'scuzzy') and USB connections are much faster than parallel ports but may require an adapter card for older computers.

TWAIN
It's whispered that TWAIN stands for Technology Without An Interesting Name. It refers to the driver that enables any scanner to communicate with any computer.