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"
the choicest or most essential or most vital part of some idea or experience; "the gist of the prosecutor's argument"; "the heart and soul of the Republican Party"; "the nub of the story"
a single whole grain of a cereal; "a kernel of corn"
the inner and usually edible part of a seed or grain or nut or fruit stone; "black walnut kernels are difficult to get out of the shell"
having a bearing on or connection with the subject at issue; "the scientist corresponds with colleagues in order to learn about matters relevant to her own research"
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"
(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