A mathematical term for a mapping between function spaces, such as a differential or integral operator.
The theory of linear operators is fundamental to functional analysis.
この微分方程式は、ある作用素の固有値問題として定式化できる。
This differential equation can be formulated as an eigenvalue problem for an operator.
Compound of 作用 (action, operation) and 素 (element, basis), likely a calque from a Western mathematical term.