Jim Thompson wrote:
I have a specification for an amplifier design that says "0.25%
linearity".

I can't seem to lay my hands on a precise definition of what that
means.

Likewise... How to calculate?

...Jim Thompson

The very word almost invariably refers to A/D errors these days, and
typically specifies 1/2LSB maximum error due to all amplifier
characteristics: offsets, gain errors, rolloff. The 0.25% would be
approximately 1/2LSB for an 8-bit.