"Necessity" refers to something that is absolutely needed or required. It is something that is essential or indispensable for a certain purpose or situation. Full definition
Today our living standards have become a costly affair with the price rise and the list of necessities of life has also extended largely with insurance becoming one of the top most priorities. (policybazaar.com)
This was facilitated at the time mostly out of necessity in order to have a strong enough club in terms of quality and to be viable financially. (footballticketpad.com)
Some of them are disposable by necessity for hygiene purposes — for instance, blood bags and other medical items — but many others are disposable for convenience. (scientificamerican.com)