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"
(computer science) the area of the screen in graphical user interfaces against which icons and windows appear
a person's social heritage: previous experience or training; "he is a lawyer with a sports background"
information that is essential to understanding a situation or problem; "the embassy filled him in on the background of the incident"
the part of a scene (or picture) that lies behind objects in the foreground; "he posed her against a background of rolling hills"
relatively unimportant or inconspicuous accompanying situation; "when the rain came he could hear the sound of thunder in the background"
extraneous signals that can be confused with the phenomenon to be observed or measured; "they got a bad connection and could hardly hear one another over the background signals"
understate the importance or quality of; "he played down his royal ancestry"
a defensive post at the end of a bridge nearest to the enemy
an area in hostile territory that has been captured and is held awaiting further troops and supplies; "an attempt to secure a bridgehead behind enemy lines"; "the only foothold left for British troops in Europe was Gibraltar"
an initial accomplishment that opens the way for further developments; "the town became a beachhead in the campaign to ban smoking outdoors"; "they are presently attempting to gain a foothold in the Russian market"
a bridgehead on the enemy's shoreline seized by an amphibious operation; "the Germans were desperately trying to contain the Anzio beachhead"