Interior means the inside part of something, the space within its outer boundaries or walls. The interior of a house includes all the rooms, hallways, and spaces where people live, while the exterior is the outside walls and roof. A car's interior is everything inside the cabin: the seats, dashboard, and floor mats.

When explorers traveled into the interior of a continent, they journeyed deep into the central regions, far from the coasts where most people lived. The vast interior of Australia was one of the last places on Earth to be thoroughly mapped by European explorers.

The word also describes something located inside rather than on the surface. An interior wall divides rooms within a building but doesn't touch the outside. Interior angles in geometry are the angles formed inside a shape.

People also use interior to talk about inner thoughts and feelings. Your interior life means your private thoughts, emotions, and imagination, the parts of yourself that others can't see from the outside. A character's interior monologue in a novel reveals what they're thinking but not saying out loud.

When used as a job title, an interior designer creates and arranges the furnishings, colors, and layout of indoor spaces to make them both beautiful and functional.