What name is given to a dam constructed from concrete and/or stone masonry and designed to hold back the water by using only the weight of the material and its resistance against the foundation?
What name is given to fluctuations in the curvature of spacetime that were predicted to exist by Albert Einstein in 1916 on the basis of his theory of general relativity?
What name is given to a special day or happening, used variously over centuries to mark important days in a calendar, to mark capitals or rubrics in religious texts, or to wear particular clothing?
