Tra từ necessary - Từ điển Oxford Advanced Learner 8th

ne·ces·sary [necessary necessaries] BrE [ˈnesəsəri] NAmE [ˈnesəseri] adjective
1. ~ (for sb/sth) (to do sth) that is needed for a purpose or a reason
Syn: ↑essential
• It may be necessary to buy a new one.
• It doesn't seem necessary for us to meet.
•Only use your car when absolutely necessary.
•If necessary, you can contact me at home.
•I'll make the necessary arrangements.
•Changes can easily be made where necessary.
•She has the qualities necessary to be a successful teacher.
2. only before noun that must exist or happen and cannot be avoided
Syn: ↑inevitable
• This is a necessary consequence of progress.
Idiom: ↑necessary evil

Word Origin:
late Middle English: from Latin necessarius, from necesse ‘be needful’.

Thesaurus:
necessary adj.
1.
•It's not necessary to buy any special equipment.
essential • • vital • • crucial • • critical • • indispensable • |informal of the essence • |formal imperative • • compulsory • • mandatory • • obligatory • • requisite •
Opp: unnecessary
necessary/essential/vital/crucial/critical/indispensable/of the essence/imperative/requisite for sth
necessary/compulsory/mandatory/obligatory for sb to do sth
necessary/essential/vital/crucial/critical/imperative/compulsory/mandatory/obligatory to do sth
necessary/essential/vital/crucial/critical/imperative that…
2. only before noun
•This is a necessary consequence of progress.
inevitable • • unavoidable • • inescapable • |formal inexorable •
Opp: avoidable
a/an necessary/inevitable/unavoidable consequence
a/an necessary/inevitable/inescapable conclusion/fact

Example Bank:
•I was determined not to stay in hospital for any longer than was strictly necessary.
•Make any alterations you consider necessary.
•The cold weather has made it necessary to protect the crops.
•These measures will be enforced, if necessary, by the army.
•We are here to give help and support when necessary.
•You may find it necessary to readjust the wheels from time to time.
•qualifications which are necessary for work with the under-fives
•A necessary condition for a steep fall in demand is a widespread collapse in confidence.
•Changes can easily be made where necessary.
•I'll make the necessary arrangements.
•If necessary, you can contact me at home.
•It doesn't seem necessary for us to meet.
•She has the necessary qualities to be a successful teacher.