Mathematically, an inflection point (IP) is simply a point at which a curve crosses its tangent, that is, where the curve changes from being concave to convex, or vice versa. At an inflection point, the curve's slope (or first derivative) reaches a local maximum or minimum and the second derivative has an isolated zero.

Prometheus thermal unfolding profiles are characteristic for a given sample (for a certain protein, under certain conditions, in a certain buffer etc.). This is true for the general shape of the unfolding profile, its directionality, its absolute values, etc, and also its IPs. If a protein's stability changes, its IPs are likely to change, too. The higher the IP, the more stable the protein. IPs therefore serve as a useful parameter for comparing protein stability across conditions, buffers, proteins and so on. In this capacity, IPs are often used interchangeably with Tms (melting points). 

Many proteins exhibit more than one unfolding event, for example proteins with several domains that unfold separately. These proteins don't have one single IP, but instead IP#1, IP#2, IP#3 etc. 

IPs are also calculated for turbidity data. In the context of turbidity data, IPs are not an established stability parameter, but can still serve for comparison for the same reasons outlined above.

Prometheus software always outputs an IP as its x-value (°C).