Definition
An Air Route Traffic Control Center (ARTCC), the FAA facility that provides air traffic control service to aircraft operating on IFR flight plans within controlled airspace, principally during the en route phase of flight. 'Center' is the standard radio call sign used when communicating with this facility.
Plain English
The controllers who handle airplanes during the long middle part of an IFR flight, after they leave the local airport area and before they get close to their destination. Pilots talk to them on the radio using the name 'Center.'
Context Anchor
Heard in radio instructions such as “contact Denver Center” or “contact Jacksonville Center.”
Derivation
From Latin 'centrum,' meaning the middle point. The name fits because these facilities handle the central, en route portion of a flight — the part between departure and arrival operations.
Why Pilots Care
Contacting the correct Center keeps your flight separated from other aircraft and provides routing and weather advisories during cruise.
Intuition Check
Do not read Center as “the middle” of something here. In this FAA meaning, Center is a regional air traffic control facility that manages aircraft over a large area.
Example Sentence 1
After departure, the tower handed us off to Center, who cleared us direct to our destination.
Example Sentence 2
After departure we contacted Center on the frequency shown on the chart.