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Tropo- is a combining form used like a prefix variously meaning “turn,” “reaction, response,” or “change.” The form is used in many scientific terms, including in biochemistry, ecology, and meteorology, where tropo- specifically represents the troposphere, the lowest layer of the atmosphere.

Tropo- ultimately comes from the Greek �ٰ�ó��Dz�, “turn,” and �ٰ��DZ�ḗ, “a turning.” The Greek �ٰ�ó��Dz� 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.

What are variants of tropo-?

When combined with words or word elements that begin with a vowel, tropo- becomes trop-, as in tropism.

Corresponding forms of tropo- combined to the end of words are -trope, -tropic, -tropism, –tropous, and –tropy. Learn about their specific applications in our �y��vlogs That Use articles for the forms.

One example of a scientific term that features tropo- is tropophyte, a term for a plant, such as a broad-leaved tree, adapted to environments that alternate between wet and dry conditions.

The first part of the word, tropo-, can indicate “change.” The second part of the word, -phyte, from the Greekn �����ó��, means “plant.” Tropophyte literally translates to “changing plant,” a reference to how it reacts to its environment.

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

• tropocollagen
• tropomyosin
• troponin (based on tropomyosin)
• tropopause
• tropophilous
• troposphere
• tropotaxis

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

• topo-
• tropho-

Using the meaning of tropo- as a clue, which layer of Earth’s atmosphere experiences the most variable, changing weather patterns?

A. troposphere

B. stratosphere

C. mesophere

D. thermosphere

E. exosphere