First Order

First order refers to a situation or process where the change or response occurs directly and immediately in reaction to a cause, without involving additional steps or complexities. For example, in chemistry, a first-order reaction depends directly on the concentration of one reactant, meaning the rate changes proportionally with that reactant's amount. In general, "first order" indicates a straightforward, primary level of response or relationship, where the effect depends directly on a single factor, making the system's behavior more predictable and simpler to analyze.