LPI
Lines per inch — how finely the grid of halftone dots is spaced when an image is printed, the print trade's counterpart to dpi.
The abbreviation stands for "lines per inch" and states the screen ruling of a halftone image: how many rows of printing dots fit per inch. A newspaper prints around 85 lpi, a glossy magazine around 150, and fine-art work up to 200. The higher the lpi, the finer the tones — but the fussier the paper and press must be.
Lpi should not be confused with dpi: dpi is how many dots the printer can physically place, lpi is how coarsely they are grouped into halftone dots. A 1200-dpi laser printer might only screen at 133 lpi, because each halftone dot is built from a small grid of dpi dots. That relationship caps how many grey levels a given resolution can render — hence the popularity of error diffusion on humbler printers.