The exponential function maps the real line (from minus infinity to plus infinity) to the range zero to plus infinity in a monotonically increasing manner. It is normally encountered in modelling when the argument is a negative number mapped from a finite positive number to zero in a monotonically decreasing manner.
| 2000 BC | Babylonians? | Compound Interest |
| 1840 AD | Farr | Farr's Law |
| 1927 AD | Kermack & McKendrick | Standard SIR model |
| 1963 AD | Mandlebrot | Cotton prices |
| 1973 AD | Black, Scholes & Merton | Black-Scholes |
| 2024 AD | Mason | Minimal SIR model |