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

/ 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

-tropism

²

combining form

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

   phototropism

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

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

From Salon

We demonstrated a yearning to correct our mistakes and, I think, a tropism toward goodness.

From New York Times

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

We decided to search for viral protein sequences that could be important for tissue tropism.

From Nature

But Leary, the “flamboyant psychology professor with a tropism bending him toward the sun of publicity” too loudly encouraged American youth to “turn on, tune in, and drop out,” and the social upheavals threatened by psychedelics proved too much for the country; all hallucinogens were banned for consumption and research by 1970.

From Salon

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!