an anatomical structure used as a point of origin in locating other anatomical structures (as in surgery) or as point from which measurements can be taken
a mark showing the boundary of a piece of land
an event marking a unique or important historical change of course or one on which important developments depend; "the agreement was a watershed in the history of both nations"
the position of a prominent or well-known object in a particular landscape; "the church steeple provided a convenient landmark"
(cryogenics) the lowest temperature theoretically attainable (at which the kinetic energy of atoms and molecules is minimal); 0 Kelvin or -273.15 centigrade or -459.67 Fahrenheit
absolutely required and not to be used up or sacrificed
absolutely necessary; vitally necessary; "essential tools and materials"; "funds essential to the completion of the project"; "an indispensable worker"
being or relating to or containing the essence of a plant etc; "essential oil"
arranged like rays or radii; radiating from a common center; "radial symmetry"; "a starlike or stellate arrangement of petals"; "many cities show a radial pattern of main highways"
issuing in rays from a common center; relating to rays of light; "radial heat"
relating to or moving along or having the direction of a radius; "radial velocity"
relating to or near the radius; "the radial aspect of the forearm"
the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes
a center of activity or interest or commerce or transportation; a focal point around which events revolve; "the playground is the hub of parental supervision"; "the airport is the economic hub of the area"