alternate vs necessity

alternate

noun
  • A substitute; an alternative; one designated to take the place of another, if necessary, in performing some duty. 

  • A replacement of equal or greater value or function. 

  • A proportion derived from another proportion by interchanging the means. 

  • That which alternates with something else; vicissitude. 

  • Figures or tinctures that succeed each other by turns. 

verb
  • To vary by turns. 

  • To perform by turns, or in succession; to cause to succeed by turns; to interchange regularly. 

  • To perform an alternation (removal of alternate vertices) on (a polytope or tessellation); to remove vertices (from a face or edge) as part of an alternation. 

  • To happen, succeed, or act by turns; to follow reciprocally in place or time; followed by with. 

adj
  • Other; alternative. 

  • Distributed singly at different heights of the stem, and at equal intervals as respects angular divergence 

  • Designating the members in a series, which regularly intervene between the members of another series, as the odd or even numbers of the numerals; every other; every second. 

  • Happening by turns; one following the other in succession of time or place; first one and then the other (repeatedly) 

necessity

noun
  • Something necessary; a requisite; something indispensable. 

  • Something which makes an act or an event unavoidable; an irresistible force; overruling power. 

  • Greater utilitarian good; used in justification of a criminal act. 

  • Indispensable requirements (of life). 

  • The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual, to inevitable causation; necessitarianism. 

  • The condition of being needy; desperate need; lack. 

  • The quality or state of being necessary, unavoidable, or absolutely requisite. 

How often have the words alternate and necessity occurred in a corpus of books? (source: Google Ngram Viewer )