An obelisk (UK: /ˈɒbəlɪsk/; US: /ˈɑːbəlɪsk/, from Ancient Greek: ὀβελίσκος obeliskos; diminutive of ὀβελός obelos, "spit, nail, pointed pillar") is a tall, four-sided, narrow tapering monument which ends in a pyramid-like shape or pyramidion at the top. These were originally called "tekhenu" by their builders, the Ancient Egyptians. The Greeks who saw them used the Greek 'obeliskos' to describe them, and this word passed into Latin and ultimately English. Ancient obelisks are monolithic; that is, they consist of a single stone. Apart from its shape, this is the major identifying characteristic of an obelisk, as it necessitates the technological ingenuity required to elevate into vertical position a massive rock weighing hundreds of tonnes.
Though this technological capacity exists today, most modern obelisks are made of several stones; some, like the Washington Monument, are buildings. Technically, these are not real obelisks, but rather obelisk-shaped monuments.
The term stele is generally used for other monumental, upright, inscribed and sculpted stones.