A catalyst is an event or person causing a change. Getting kicked out of your parents' house might be a catalyst for becoming more independent.

The noun catalyst is something or someone that causes a change and is derived from the Greek word katalύein, meaning "to dissolve." It can be somewhat ordinary, like when moving to a warmer climate was the catalyst for getting a short, sporty haircut. Or it can be major, like how the assassination of Archduke Franz Ferdinand of the Austro-Hungarian Empire is said to be a catalyst of World War I.

Definitions of catalyst
  1. noun
    (chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected
    synonyms: accelerator
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    (chemistry) a substance that retards a chemical reaction or diminishes the activity of a catalyst
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    a biochemical catalyst such as an enzyme
    any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions
    platinum black
    a fine black powder of platinum; used as a catalyst in chemical reactions
    ADA, adenosine deaminase
    an enzyme found in mammals that can catalyze the deamination of adenosine into inosine and ammonia
    any of a group of proteins found in saliva and pancreatic juice and parts of plants; help convert starch to sugar
    an enzyme that hydrolyses acetylcholine (into choline and acetic acid)
    an enzyme that induces coagulation
    any enzyme that catalyzes the hydrolysis of collagen and gelatin
    one of a series of enzymes in the blood serum that are part of the immune response
    enzyme found in most plant and animal cells that functions as an oxidative catalyst; decomposes hydrogen peroxide into oxygen and water
    Cox, cyclooxygenase
    either of two related enzymes that control the production of prostaglandins and are blocked by aspirin
    any of the enzymes that hydrolize the carboxyl group
    an enzyme that removes the iodine radical
    an enzyme that catalyzes the hydrolysis of disaccharides into monosaccharides
    a pancreatic enzyme that catalyzes the hydrolysis of elastin
    enzyme in the intestinal juice that converts inactive trypsinogen into active trypsin
    enzyme that acts as a catalyst in converting histidine to histamine
    Hyazyme, hyaluronidase, spreading factor
    an enzyme (trade name Hyazyme) that splits hyaluronic acid and so lowers its viscosity and increases the permeability of connective tissue and the absorption of fluids
    an enzyme that catalyzes its substrate to an isomeric form
    an enzyme that catalyzes the conversion of a proenzyme to an active enzyme
    an enzyme secreted in the digestive tract that catalyzes the breakdown of fats into individual fatty acids that can be absorbed into the bloodstream
    lysozyme, muramidase
    an enzyme found in saliva and sweat and tears that destroys the cell walls of certain bacteria
    MAO, monoamine oxidase
    an enzyme that catalyzes the oxidation of many body compounds (e.g., epinephrine and norepinephrine and serotonin)
    an enzyme of nitrogen-fixing microorganisms that catalyzes the conversion of nitrogen to ammonia
    general term for enzymes that catalyze the hydrolysis of nucleic acid by cleaving chains of nucleotides into smaller units
    any of the enzymes that catalyze biological oxidation
    an enzyme that catalyzes oxidation-reduction
    a proteolytic enzyme obtained from the unripe papaya; used as a meat tenderizer
    beta-lactamase, penicillinase
    enzyme produced by certain bacteria that inactivates penicillin and results in resistance to that antibiotic
    an enzyme produced in the stomach that splits proteins into peptones
    precursor of pepsin; stored in the stomach walls and converted to pepsin by hydrochloric acid in the stomach
    any of a group of enzymes that act as a catalyst in the hydrolysis of organic phosphates
    fibrinolysin, plasmin
    an enzyme that dissolves the fibrin of blood clots
    an enzyme that catalyzes the formation of new DNA and RNA from an existing strand of DNA or RNA
    peptidase, protease, proteinase, proteolytic enzyme
    any enzyme that catalyzes the splitting of proteins into smaller peptide fractions and amino acids by a process known as proteolysis
    an enzyme that catalyses the biochemical reduction of some specified substance
    chymosin, rennin
    an enzyme that occurs in gastric juice; causes milk to coagulate
    a set of enzymes believed to snip pieces off a longer protein producing fragments of amyloid protein that bunch up and create amyloid protein plaques in brain tissue (the pathological hallmark of Alzheimer's)
    an enzyme produced by some hemolytic strains of streptococcus that dissolves fibrinous secretions from infections; used medicinally (often in combination with streptokinase)
    an enzyme produced by some strains of streptococcus that can liquefy blood clots by converting plasminogen to plasmin; used medicinally in some cases of myocardial infarction and pulmonary embolism
    SOD, superoxide dismutase
    an enzyme that catalyzes the conversion of superoxide into hydrogen peroxide and oxygen
    an enzyme in eukaryotic cells that can add telomeres to the ends of chromosomes after they divide
    any of various enzymes that move a chemical group from one compound to another compound
    an enzyme of pancreatic origin; catalyzes the hydrolysis of proteins to smaller polypeptide units
    an enzyme that catalyzes the hydrolysis of urea into carbon dioxide and ammonia; is present in intestinal bacteria
    a complex of enzymes that cause glycolysis; originally found in yeast but also present in higher organisms
    type of:
    (biology) any agency bringing about activation; a molecule that increases the activity of an enzyme or a protein that increases the production of a gene product in DNA transcription
  2. noun
    something that causes an important event to happen
    “the invasion acted as a catalyst to unite the country”
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    type of:
    causal agency, causal agent, cause
    any entity that produces an effect or is responsible for events or results
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