| noun | anything indispensable “food and shelter are necessities of life” |
| adjective | absolutely necessary; vitally necessary “essential tools and materials” |
| adjective | basic and fundamental “the essential feature” |
| adjective | of the greatest importance “the all-important subject of disarmament” |
| adjective | being or relating to or containing the essence of a plant etc “essential oil” |
| adjective | defining rights and duties as opposed to giving the rules by which rights and duties are established “substantive law” |
| necessitous | adjective | poor enough to need help from others |
| necessary | adjective | absolutely essential |
| necessitate | verb | require as useful, just, or proper |
| essential | adjective | absolutely necessary; vitally necessary |
| require | verb | have need of |
| requisite | adjective | necessary for relief or supply |
| essential | noun | anything indispensable |
| essentialness | noun | basic importance |
| indispensableness | noun | the quality possessed by something that you cannot possibly do without |
| indispensability | noun | the quality possessed by something that you cannot possibly do without |
| essentiality | noun | basic importance |
| cruciality | noun | a state of critical urgency |
| essence | noun | the choicest or most essential or most vital part of some idea or experience |