Stability can be defined in many ways based on what the applied stress is. In most  cases, stability is inferred based on the protein’s melting temperature (Tm).  If a protein can withstand higher temperatures without unfolding, that protein is said to be more stable. There are multiple tools for measuring melting temperature including DSF, DSC, and CD.
Quantification of stability through the melting temperature determined by differential scanning fluorimetry (DSF)
The figure above shows the quantification of stability through the melting temperature determined by differential scanning fluorimetry (DSF). The melting temperature is the temperature that causes the protein to be halfway unfolded, and the higher the melting temperature, the more stable the protein.  This figure shows that the melting temperature increases when it’s bound to a  ligand. (Samuel, Errol LG, et al.) "Processing binding data  using an open-source workflow." Journal of Cheminformatics 13.1  (2021): 1-11.)
However,  there are many other forms of stress other than temperature such as agitation, pH, pressure, light exposure etc. It is also important to understand the structure and stability of a biologic under all likely production conditions. MMS is another tool that can measure the protein structure after being exposed to any of these stresses and that can help predict the protein stability.
‍