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  

combining form

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

   phototropism

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tropism ² 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 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

-tropy, -ism

Example Sentences

“The lack of efficient lung tropism in previous Omicron lineages contributed to their mild presentation without immediate hospitalization requirements.”

From Salon • Jan. 12, 2024

The movement of a plant subjected to constant directional pressure is called thigmotropism, from the Greek words thigma meaning “touch,” and tropism implying “direction.”

From Textbooks • Jun. 9, 2022

Yet the most consistent and powerful sense at Armani shows is of a tropism toward the war years and the images of them that he has retained.

From New York Times • Jan. 15, 2020

How strange it would be, then, that this accident, this excess, should feel a tropism toward what Pinker himself calls "the truth".

From The Guardian • Jun. 4, 2010

Tactism and Tropism.—The phenomena of tactism and tropism may also be partly explained by the action of these diffusion currents of particles in suspension, these polar attractions and repulsions.

From The Mechanism of Life by Leduc, Stéphane