Extrapolate
Etymology
A 19th-century coinage built by analogy with “interpolate,” swapping its “inter-” (between) for “extra-” (beyond), on the Latin “polire,” to polish or furbish. So it is a word deliberately modeled on an older one, and it inherits the same faint warning: a value invented rather than measured.
verb · /ik-STRAP-uh-layt/
To extend a known pattern beyond the data to estimate what lies outside it.
What it names
Reasoning past the edge of the evidence — projecting a trend forward or outward into the unobserved.
Example
From two data points they extrapolated a growth curve that reality never came close to matching.
Related idea
To extrapolate is to reach beyond the known range; to interpolate is to estimate within it. Extrapolation is the riskier move — the ground it stands on runs out.
See also