Adobe is a building material made from soil and often organic matter. Adobe means mudbrick in Spanish. It can also mean any kind of earth construction.
Adobe is one of the earliest building materials ever used. It is found all over the world. The techniques used in adobe construction have not changed since the 16th century in the Southwestern United States. Because they are not fired in a kiln they never become hard. They shrink and swell as the water content in them changes. Also, as they get wetter, they become weaker.