Complex sentence: Together with James Clerk Maxwell and Ludwig Boltzmann, Gibbs founded "statistical mechanics", a term that he coined to identify the branch of theoretical physics that accounts for the observed thermodynamic properties of systems in terms of the statistics of large ensembles of particles.
Split into simpler sentences: Together with James Clerk Maxwell and Ludwig Boltzmann, Gibbs is considered one of the founders of statistical mechanics. It was Gibbs who coined the term "statistical mechanics" to identify the branch of theoretical physics that accounts for the observed thermodynamic properties of systems in terms of the statistics of large ensembles of particles.