contraction vs slackening

contraction

noun
  • Syncope, the loss of sounds from within a word. 

  • The acquisition of something, generally negative. 

  • A period of economic decline or negative growth. 

  • A process whereby one or more sounds of a free morpheme (a word) are lost or reduced, such that it becomes a bound morpheme (a clitic) that attaches phonologically to an adjacent word. 

  • A strong and often painful shortening of the uterine muscles prior to or during childbirth. 

  • A shorthand symbol indicating an omission for the purpose of brevity. 

  • A reversible reduction in size. 

  • A word with omitted letters replaced by an apostrophe, usually resulting from the above process. 

  • The process of contracting a disease. 

  • A distinct stage of wound healing, wherein the wound edges are gradually pulled together. 

  • A shortening of a muscle during its use. 

slackening

noun
  • The act by which something slackens; loss of speed, tautness, etc. 

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