What does approximation mean?
An approximation is a value, estimate, or description that comes close to something without matching it exactly. The word belongs most naturally to mathematics, science, and engineering, where complex quantities are routinely simplified — treating a curve as a straight line, or pi as 3.14 — so that problems become tractable. Yet its use extends well beyond technical fields: people speak of a rough approximation of the truth, or note that a copy is only an approximation of the original. The word carries no strong connotation of error; rather, it acknowledges that near-enough answers are often all that reality permits, and frequently all that is needed. Phrases such as 'a close approximation' and 'a first approximation' are firmly established, the latter even serving metaphorically to mean a basic starting guess. Understanding approximation means understanding one of the central strategies of human reasoning: settling for the nearly right when the exactly right is unavailable.
nounA value, estimate, or description that is close to but not exactly equal to something else; the act or process of estimating or coming close to a desired result.
- A value or statement that is close to but not exactly correct (e.g. a numerical estimate).
- The act or process of estimating or coming close to something.
"The engineer's approximation of the load was close enough for the design to proceed."
"As a first approximation, we can treat the Earth as a perfect sphere."
"Her translation is only an approximation of the original poem's meaning."
The plural is standard and common, especially in mathematics and science when referring to multiple estimates or successive stages of refinement.
"Newton's method generates successively better approximations of the root."
Every number you've ever used to describe the real world — from pi to your height — is an approximation; exactness is the rare exception.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of approximation
Approximation derives from the Latin 'approximare', meaning 'to approach or come near', formed from 'ad-' ('toward') plus 'proximus' ('nearest'), the superlative of 'prope' ('near'). The word entered English in the early modern period, with the verb 'approximate' attested from the early 17th century and the noun following shortly after. It shares this root with 'proximate', 'proximity', and 'approach', all pointing back to the same Latin idea of nearness.
Related word forms
How approximation is actually used
Common in mathematics, science, and engineering, where 'first approximation' and 'close approximation' are standard technical phrases. Also used figuratively for imprecise descriptions ('a rough approximation of the truth'). Register is neutral to formal.
Easily confused with approximation
Estimation is the act of judging or calculating a value, while approximation is the resulting near-match itself — though in practice the two overlap heavily.