What does sextant mean?
A sextant is an instrument used to measure angles, especially the angle between a celestial body and the horizon. Its name comes from its graduated arc, which covers one-sixth of a circle, or 60 degrees. Navigators use a sextant with the sun, stars, or other celestial objects to determine latitude; a similar observation can help establish a ship's position. The instrument developed from earlier navigational devices, including the quadrant, and became especially important at sea before accurate electronic positioning systems became widely available. Although modern navigation relies heavily on satellite-based tools, the sextant remains a notable example of a compact mechanical instrument that enables sophisticated astronomical measurement. The word can also be used more generally for certain surveying and astronomical instruments that measure angles.
nounA navigational instrument used to determine latitude or the angle between a celestial object and the horizon. It consists of an arc covering one-sixth of a circle, with mirrors and sighting mechanisms for precise measurement.
- A nautical instrument with a graduated arc of 60 degrees, used to measure the angle of a celestial body above the horizon in order to determine a ship's position.
- Any instrument, especially one used in surveying or astronomy, designed to measure angles by means of an arc and a movable index.
"The navigator adjusted the sextant and took a careful reading of the midday sun."
"Using a sextant, she calculated the ship's latitude from the angle of the noon sun."
"The surveyor used a sextant to measure the angle between two distant landmarks."
The plural is formed by adding -s to the word.
"The crew stored the sextants in a padded case."
Before GPS, finding your way at sea often meant a navigator had to read the angle of the sun or stars through a sextant.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sextant come from?
The word comes from the Latin sextans, meaning “a sixth part,” a noun derived from sextus, “sixth.” The instrument was named because its arc measured one-sixth of a circle. Its name is therefore related to other English words based on the Latin numeral sex, such as sextuple and sexagenary. The sextant developed from earlier angle-measuring navigational instruments and reached its familiar form in the eighteenth century.
Related word forms
How sextant is actually used
In everyday nautical use, the term specifically refers to a compact navigational instrument. In surveying and astronomy, it can refer more broadly to angle-measuring instruments, though other names are often preferred in those fields.
Easily confused with sextant
A sextant is an instrument for measuring angles, whereas a sextet is a group of six people or musical performers.