anticommutator

This term is used exclusively within the highly specialized registers of quantum mechanics and abstract algebra. It describes a specific algebraic operation that differs from a commutator by using addition instead of subtraction, which is a critical distinction when dealing with fermions in physics.

Because it refers to a specific mathematical object or operator, it is treated as a standard countable noun. It is almost never used outside of technical academic papers or textbooks focusing on operator theory or particle physics.