Adjectival nouns or quasi-adjectives (keiyodoshi); 必用 can imply has to be used rather than is just needed

necessary; needed; essential; indispensable

Common noun

necessity; need; requirement

always; without exception; necessarily; certainly; without fail; positively; invariably

Adjectival nouns or quasi-adjectives (keiyodoshi); Nouns which may take the genitive case particle 'no'

frantic; frenetic; desperate

Common noun

inevitable death

Common noun; Shogi

brinkmate (inevitable checkmate)

unnecessary; not needed; not necessary

to need; to call for; to require

With neg. sentence

(not) always; (not) necessarily; (not) entirely; (not) all

desperately; for one's dear life

Nouns which may take the genitive case particle 'no'; Adjectival nouns or quasi-adjectives (keiyodoshi)

inevitable; necessary; certain; sure

Common noun

inevitability; necessity

indispensable; essential; requisite; required; compulsory; necessary

inevitable; necessary