Trajectory
TRAJ-ik-ter-ee
/ˈtrædʒɪktəri/
The path followed by a projectile flying or an object moving under the action of given forces.
A trajectory is typically curved due to forces like gravity and air resistance. It describes the entire path, not just the starting and ending points.
The story behind the word. "Trajectory" comes from the Latin "trajectoria," meaning "a throwing across." It's derived from "trajectus," the past participle of "trajicere," which means "to throw across." This combines "trans-" (across) and "jacere" (to throw), perfectly describing the path of something thrown.
Word relationships
- path: "Path" is a more general term for a route; "trajectory" specifically implies a path taken by a moving object under forces.
- course: "Course" can refer to a planned route or direction, but "trajectory" is the actual, often curved, physical path.
- stationariness: The state of being still, having no path of motion.
- randomness: Lack of a predictable or defined path.
Commonly confused with
- Direction: Direction is a single vector; trajectory is the entire sequence of positions over time, forming a path.
Word family
- project (verb): To throw forward.
- projectile (noun): An object thrown or fired.
Collocations
- parabolic trajectory
- ballistic trajectory
- flight trajectory
- orbital trajectory
- alter trajectory
Idioms & expressions
- on a collision trajectory
Example sentences
- "The quarterback threw a perfect spiral, and the ball followed a precise trajectory to the receiver." Describing a ball's flight.
- "Engineers carefully calculated the spacecraft's trajectory to ensure a successful lunar orbit insertion." From a space mission report. (NASA Mission Report)
Memory hook
TRAJECTORY is the path a TRAIN takes across the country. Train Path
When not to use
While "trajectory" can be used metaphorically (e.g., "career trajectory"), ensure the context is clear if you mean the physical path.
Fun facts
- The study of trajectories is crucial in ballistics, space travel, and sports.
- In a vacuum, a projectile's trajectory under gravity is a perfect parabola.
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