necessity

necessity /nɪˈsɛsəti/ noun
plural necessities
necessity
/nɪˈsɛsəti/
noun
plural necessities
Britannica Dictionary definition of NECESSITY
1 
[count] : something that you must have or do : something that is necessary
2 
[noncount] formal : the quality of being necessary — usually + of or for

by necessity

or out of necessity
: because of conditions that cannot be changed

make a virtue (out) of necessity

— see virtue

necessity is the mother of invention

— see 1mother

of necessity

formal
— used to say that something must happen or must be the way it is