A surface is the outer part of something. Most surfaces have a width and a length, but no depth.^[1]

Surfaces are studied in geometry.

Examples of Surfaces

• An apple has a skin on its surface.
• People live on the Earth's surface.
• A piece of metal is put in red paint. The metal is taken out of the paint. After, the outside of the piece of metal is red. The parts of the metal that are now red are called the surface of the object.
• Boats move on the surface of the sea.
• Small insects can walk on the surface of the water, because of surface tension.