Parallax
Etymology
From Greek "parallaxis" ("alteration"), via "parallassein" ("to alter"), from "para-" ("beside") plus "allassein" ("to change"), rooted in "allos" ("other"). Astronomers use the tiny parallax of a star, measured across Earth’s orbit, to calculate its distance — turning a shift in viewpoint into a ruler.
noun · /PA-ruh-laks/
The apparent shift in an object’s position when you view it from two different vantage points.
What it names
A precise word for how perspective itself changes what you see — and, by extension, how comparing two viewpoints can reveal depth that neither shows alone.
Example
Rereading the letters years later gave her a parallax on her parents’ marriage she could never have had at the time.
Related idea
Where perspective is any single point of view, parallax is specifically the difference between two of them — the gap that lets you triangulate the truth.