I need a good definition for span and linearity on pressure gauges.

[USMCPMEL]

I am arguing with a technician about what the two words means. I want to see what our community has to say about it.

[USMC kalibrater]

span is related to range as the sum of two vectors and linearity is the graphical representation of how the gauge indicates actual compared to measured. 

[BamaKid]

The Metrology Handbook, by ASQ does a nice job of addressing these two terms:
Linearization:  a method by which IMTE is corrected for a linear response such that a step change in an applied signal will result in a corresponding step change in the IMTE indication. Linearization is typically used to correct for nonlinear measurement sensors such as those used to make high temperature measurement.

Spanning: is a method by which an IMTE specific range is defined. Spanning typically involves bringing an IMTE measurement readout scale in agreement with intended range of the unit via adjustments, changing component values, or firmware correction. Spanning helps ensure that a unit's high, low, and mid-range measurement responses correspond to its high, low, and mid-scale measurement readout values. This method is commonly used to set up the range of a pressure gauge.