unnecessary; not needed; not necessary
to need; to call for; to require
absolutely essential; indispensable; vital; critical
bare minimum; minimum necessary (amount, number, etc.)
unnecessary; not needed; not necessary
necessary condition; requirement
necessary information; required fields (e.g. in a form)
necessary documents; important documents
necessity is the mother of invention
necessary and sufficient condition
(socially) necessary labour; necessary work
as necessary (needed); if necessary (needed)
necessary labour time (in Marxian economics)
(minimum) system requirements