NECESSARY
—adjective. 1 requiring to be done; requisite, essential. 2 determined, existing, or happening by natural laws etc., not by free will; inevitable. —none. (plural. -ies) (usually. In plural.) Any of the basic requirements of life. ? the necessary colloq. 1 money. 2 an action etc. Needed for a purpose. ? necessarily adverb. [latin necesse needful]