Final answer:
The roof with a steep slope on two sides and commonly used on barns is a Gambrel roof. It is recognizable for its characteristic appearance and offers additional enclosed space.
Step-by-step explanation:
A gambrel or gambrel roof 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 steep. This design provides the advantages of a sloped roof while maximizing headroom inside the building's upper level and shortening what would otherwise be a tall roof. The name comes from the Medieval Latin word gamba, meaning horse's hock or leg.
The kind of roof that is a variation of the gable roof, has a steep slope on two sides, and is commonly used on barns is known as a Gambrel roof. The gambrel roof is easily identified by its characteristic design, which resembles the roof of a classic barn. This roof style provides more room under the roof, which was beneficial for storing hay or equipment in barns. Over time, this style also appeared in residential architecture, as it offers extra living space in the attic or upper floors without the need for complete additional stories.