• the point that is equally distant from every point on the circumference of a circle or sphere

• the point from which an activity or process is directed, or on which it is focused

Synonyms: foundation, basis, keystone, mainspring, mainstay, linchpin, bedrock, fundament, base, key, fundamental principle, main ingredient, central component, centrepiece, core, heart, centre, focus, crux, prop, backbone, anchor

• a place or group of buildings where a specified activity is concentrated

Synonyms: establishment, centre, installation, place, depot, station, location, premises, site, post, base, camp

• occur mainly in or around (a specified place)

• place in the middle