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"
fix conclusively or authoritatively; "set the rules"
fix in scope; fix the boundaries of; the tree determines the border of the property
shape or influence; give direction to; "experience often determines ability"; "mold public opinion"
establish after a calculation, investigation, experiment, survey, or study; "find the product of two numbers"; "The physicist who found the elusive particle won the Nobel Prize"
find out, learn, or determine with certainty, usually by making an inquiry or other effort; "I want to see whether she speaks French"; "See whether it works"; "find out if he speaks Russian"; "Check whether the train leaves on time"