Past exam of the mathematics course of the University of Cambridge / 2019 / iii / Paper 121 / 1 / i / f / Solution

N. A larger model may collapse a singular cardinal number, destroying cardinalhood, so the assertion is not described by an upward absolute formula. It may instead add a short cofinal function to a regular cardinal in the smaller model, so it is not described by a downward absolute formula. This is the nonabsoluteness of singular cardinalhood.