1) In information technology as elsewhere, a nit (pronounced NIHT) is a small, usually unimportant imperfection in something. People who have unusually high or unreasonable standards for the quality of a thing are sometimes referred to as nitpickers.
2) In lighting, the nit is a unit of visible-light intensity, commonly used to specify the brightness of a cathode ray tube or liquid crystal display computer display. One nit is equivalent to one candela per square meter. The candela, formerly called candlepower, is approximately the amount of light emitted by a common tallow candle; technically it is the quantity of radiation emitted by 1.667 x 10-6 square meter of a blackbody at the melting point of platinum. The candela is equal to one lumen per steradian (unit solid angle). (A blackbody is an object that radiates energy with 100 percent efficiency at all electromagnetic wavelengths. It also absorbs all electromagnetic energy that strikes it, hence the expression "black." It is a theoretical ideal of interest in physics and engineering.)
The nit is a comparatively small unit of brightness. A typical active-matrix LCD panel has an output between 200 and 300 nit, for example.
3) In digital electronics, the term nit is occasionally used to represent an amount, or increment, of data equal to 1.44 binary digit.