tropism

¹

[ troh-piz-uhm ]

noun

, Biology.

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

-tropism

²

1. variant of -tropy.

-tropism

¹

combining form

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

   phototropism

tropism

²

/ ˈtrəʊpɪzəm; trəʊˈpɪstɪk /

noun

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

tropism

/ 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

Derived Forms

• ˌtropisˈmatic, adjective
• tropistic, adjective

Other Words From

• tro·pis·mat·ic [troh-piz-, mat, -ik], adjective
• tro·pis·tic [troh-, pis, -tik], adjective

Word History and Origins

Origin of tropism¹

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

Origin of tropism²

-tropy, -ism

Word History and Origins

Origin of tropism¹

from Greek tropos a turn

Origin of tropism²

from Greek tropos a turn

Example Sentences

In those two books, the existential shows itself gradually—breast cancer in the first, a physiological tropism in the second.

From The Daily Beast

Still, Cuccinelli has shown his own tropism toward the kindness of strangers.

From The Daily Beast

This may be a tropism (stereotropism) or it may be a mere surface tension phenomenon.

From Project Gutenberg

It's the same old disregard, or it's the same old psycho-tropism, or process of assimilation.

From Project Gutenberg

We shall in the succeeding series of papers deal with the subject of tropism in general.

From Project Gutenberg

The workers, on the other hand, who have to be in and out of the nest about their business, do not have this tropism.

From Project Gutenberg

Nevertheless this is the psycho-tropism of science to all "thunderstones" said to have fallen luminously.

From Project Gutenberg

Words That Use -tropism

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.

Examples of -tropism

One example of a biological term that features –tropism is chemotropism, meaning “oriented growth or movement, especially of a plant, in response to a chemical stimulus.”

The first portion of the word, chemo-, means “chemical.” The second portion of the word, –tropism, indicates “turned toward.” Chemotropism literally translates to “turned towards a chemical.”

What are some words that use the combining form -tropism?

• aeolotropism
• allotropism
• anemotropism
• anisotropism
• azeotropism
• chronotropism
• cytotropism
• geotropism
• heliotropism
• hydrotropism
• plagiotropism
• plasmotropism
• sitotropism

What are some other forms that -tropism may be commonly confused with?

• -tomy
• -troph
• -trophic
• -trophy

Break it down!

The combining form helio- means “sun.” Heliotropism can refer to plants whose flowers do what?

Hint: sunflowers are known for this quality!