What is the meaning of contraction?

noun

• Physiology) a shortening or tensing of a part or organ (especially of a muscle or muscle fiber. ()
  • synonyms: muscular contraction, muscle contraction
• The process or result of becoming smaller or pressed together.
  • usage: "the contraction of a gas on cooling"
  • synonyms: compression, condensation
• A word formed from two or more words by omitting or combining some sounds.
  • usage: "`won't' is a contraction of `will not'"; "`o'clock' is a contraction of `of the clock'"
• The act of decreasing (something) in size or volume or quantity or scope. .