MINUIT

Minuit is the French word for midnight, the middle of the night. The term also appears as a surname and as the name of a widely used numerical software package for function minimization in high-energy physics.

MINUIT was developed at CERN as a general-purpose tool for finding the minimum of a function of several variables and for estimating parameter uncertainties. It provides robust algorithms designed for complex, multi-parameter fits common in physics analyses. The package includes several distinct methods: MIGRAD, a gradient-based minimization algorithm; SIMPLEX, the Nelder–Mead simplex method; HESSE, which computes the second derivatives to estimate the covariance matrix; and MINOS, which produces asymmetric parameter errors from the profile of the function.

Originally implemented in Fortran, MINUIT later evolved into MINUIT2, a C++ reimplementation that is part of the ROOT framework. Python bindings and other wrappers exist, enabling use from modern data analysis workflows. Typical usage involves defining a function to minimize (often a chi-squared or negative log-likelihood), selecting an initial parameter set, running MIGRAD to locate the minimum, and then using HESSE to obtain the covariance matrix and MINOS to determine asymmetric uncertainties when appropriate.

Impact and usage: MINUIT became a de facto standard in particle physics fitting and influenced the design of later numerical optimization tools. It remains available through MINUIT2 and various language bindings, keeping it in use for legacy analyses and educational purposes.

In non-technical contexts, minuit also signifies midnight in French. The term can thus refer to time concepts, a surname, or the suite of optimization tools developed for scientific data analysis.