A gambrel (also known as a Dutch gambrel) is a usually symmetrical two-sided roof with two slopes on each side. The upper slope is positioned at a shallow angle while the lower slope is quite steep. This design provides the advantages of a sloped roof while maximizing head space on the building's upper level. The name comes from the Medieval Latin word gamba meaning hoof, or leg of an animal.
It is not uncommon for a gambrel roof to be referred to as a Mansard roof, although the more precise usage of the terms gambrel and Mansard is that a gambrel roof applies the two-slope idea to only two sides of the building (forming gables), whereas a Mansard roof applies the two-slope idea to all four sides of the building (forming hips). It is also not uncommon for laypeople not versed in architectural terms to refer to a gambrel roof as a barn roof (because gambrels are often mentally associated with barns).