outermost

Outermost is a relative adjective formed from outer and most. It denotes something located farthest from the center, core, boundary, or inside of a system. The term is commonly used to describe the most external part of an object, region, or structure, such as the outermost edge of a circle or the outermost layer of a material.

In geography and regional planning, outermost describes peripheral zones such as the outermost suburbs of a city. In astronomy and planetary science, the outermost planet of the Solar System is Neptune; the term also applies to outermost rings or moons around a planet. In atmospheric science, Earth’s exosphere is often described as the outermost layer, gradually fading into space.

In atomic and molecular contexts, the outermost electrons occupy the valence shell and determine chemical reactivity and bonding patterns. In computing and mathematics, the outermost loop around inner iterations or the outermost parentheses can determine the scope of expressions or the order of operations.

The term remains widely used across disciplines to indicate the farthest external position within a given system, from physical boundaries to conceptual outlines.