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"
a unifying idea that is a recurrent element in a literary or artistic work; "it was the usual `boy gets girl' theme"
(music) melodic subject of a musical composition; "the theme is announced in the first measures"; "the accompanist picked up the idea and elaborated it"
provide with a particular theme or motive; "the restaurant often themes its menus"
(astronomy) the particular appearance of a body's state of illumination (especially one of the recurring shapes of the part of Earth's moon that is illuminated by the sun); "the full phase of the moon"
(physical chemistry) a distinct state of matter in a system; matter that is identical in chemical composition and physical state and separated from other material by the phase boundary; "the reaction occurs in the liquid phase of the system"
a particular point in the time of a cycle; measured from some arbitrary zero and expressed as an angle
any distinct time period in a sequence of events; "we are in a transitional stage in which many former ideas must be revised or rejected"
adjust so as to be in a synchronized condition; "he phased the intake with the output of the machine"