necessity

The condition or quality of being necessary.

Something necessary.

Something dictated by invariable physical laws.

The force exerted by circumstance.

The state or fact of being in need.

Pressing or urgent need, especially that arising from poverty.

(of necessity) As an inevitable consequence; necessarily.

The condition or quality of being necessary or needful; the mode of being or of truth of that which is necessary; the impossibility of the contrary; the absolute character of a determination or limitation which is not merely without exception, but which would be so in any possible state of things; absolute constraint.