line-of-sight
UK[ˌlaɪn əv ˈsaɪt]US[ˌlaɪn əv ˈsaɪt]
n
An unobstructed straight line between an observer and a target or point of interest.
n
The transmission path for electromagnetic waves (e.g., radio, light) that requires a direct, clear path between transmitter and receiver.
Morpheme Breakdown
line
of
sight
line
path
of
connecting preposition
sight
vision
Etymology
The compound term "line-of-sight" is a modern English formation built from native Germanic and Latinate elements to describe a geometric and perceptual concept. The word "line" evolved from the Latin līnea, originally a linen thread used for measuring, which came to signify any straight, continuous mark. "Sight" originates from Old English, related to the act of seeing. When combined in the 17th century, the phrase literally means "a line belonging to sight," logically describing the direct, unobstructed visual path between an observer and an object. This concrete meaning was later extended into physics and engineering to describe the propagation path of waves, such as light or radio signals, which travel in straight lines unless reflected or refracted.
Analysis
Structure: line (path) + of (connecting preposition) + sight (vision)
line: From Old English līne (rope, series), from Latin līnea (linen thread, string). Functions as the core noun denoting a linear path or connection.
of: From Old English of, a preposition indicating origin, separation, or relationship. Functions as a grammatical connector in the compound.
sight: From Old English siht, gesiht (thing seen, faculty of seeing), from Proto-Germanic sihtiz. Functions as a noun specifying the sense of vision.
Examples
To see the distant lighthouse, you need a clear line-of-sight from the cliff.
The microwave radio link failed because a new building blocked the line-of-sight between the towers.
The sniper adjusted his position to establish a direct line-of-sight with the target.