The Langmuir isotherm is a model that describes how molecules adsorb onto a solid surface. It assumes that adsorption occurs at specific sites on the surface and that each site can hold only one molecule. This model is often used in chemistry and materials science to understand how gases or liquids interact with solid materials. The isotherm is represented mathematically by a simple equation that relates the amount of adsorbate on the surface to its concentration in the surrounding phase. It helps predict how changes in conditions, like temperature or pressure, affect the adsorption process, making it valuable for applications in catalysis and environmental science.