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The term skew, generally referring to some difference from an expected or optimal value, is common in both telecommunications and mathematics.Skew has also acquired a new meaning for computer disk drives.
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Telecommunication
Note: Skew is usually interpreted to mean the difference in reading times between bits recorded on the tracks at the extremities, or edges, of the tape.
In facsimile systems, the angular deviation of the received frame from rectangularity caused by asynchronism between the scanner and the recorder.
Note: Skew is expressed numerically as the tangent of the deviation angle.
In facsimile, the angle between the scanning line, or recording line, and the perpendicular to the paper path.
Example of +1 degree (counter-clockwise) skew in a facsimile image. The red line is perfectly horizontal.
Source: from Federal Standard 1037C and from MIL-STD-188
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Computers
In reference to computer disk drives, track-to-track skew is the angle between the start of the data on a given track and the start of the data on the next. It's important because, when reading the data in sequence from one track to the next, time must be allowed for the read/write head to move to the next track, during which the disk continues to rotate. Insufficient skew can force the drive to wait almost an entire revolution for the data to pass under the head again, resulting in extra revolutions per track to read the data. Excessive skew can also lower the sustained data transfer rate.
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Computer graphics
Skew is a common term for the shear transformation.
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Mathematics
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