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• tropism
  tropism

  noun

  an orientation of an organism to an external stimulus, as light, especially by growth rather than by movement.
• -tropism
  -tropism

  variant of -tropy.

tropism

¹ American  

[troh-piz-uhm] / ˈtroʊ pɪz əm /

noun

Biology.

1. an orientation of an organism to an external stimulus, as light, especially by growth rather than by movement.

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-tropism ² American  

1. variant of -tropy.

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tropism ¹ British  

/ trəʊˈpɪstɪk, ˈtrəʊpɪzəm /

noun

1. the response of an organism, esp a plant, to an external stimulus by growth in a direction determined by the stimulus

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-tropism ² British  

combining form

1. indicating a tendency to turn or develop in response to a certain stimulus

   phototropism

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tropism Scientific  

/ trō′pĭz′əm /

1. The growth or movement of a living organism or anatomical structure toward or away from an external stimulus, such as light, heat, or gravity.

2. See also geotropism hydrotropism phototropism

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Usage

What does -tropism mean? The combining form -tropism is used like a suffix to form abstract nouns corresponding to adjectives ending in -tropic and -tropous, such as how neurotropism is the quality of being neurotropic. These endings variously denote “turning, changing, reacting, responding.” Learn more about -tropic and -tropous at our Words That Use articles for the forms. Where does -tropism come from?The form -tropism comes from the Greek trópos, “turn," and tropḗ, "a turning,” combined with -ism, a prolific suffix also derived from Greek that commonly indicates “action, practice, state, condition.”The biology term tropism, "an orientation of an organism to an external stimulus, as light, especially by growth rather than by movement,” is an independent use of the combining form -tropism. The Greek trópos is also the source of the words trope and tropical. It’s your turn to make the connection between “turning,”  figures of speech, and the tropics at our entries for the words. The combining form -tropism is a variant of -tropy, as in allotropy. Want to know more? Read our Words That Use -tropy article. Corresponding forms of -tropism combined to the beginning of words are tropo- and trop-, which you can also learn more about at our Words That Use articles for the forms.

Other Word Forms

• tropismatic
  adjective
• tropistic
  adjective

Etymology

Origin of tropism¹

First recorded in 1895–1900; independent use of -tropism

Origin of -tropism²

see origin at -tropy, -ism