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Astro- is a combining form used like a prefix meaning “related to stars, celestial bodies, and outer space.” It is often used in scientific terms, especially in—you guessed it—astronomy.

Astro– is also sometimes used to refer to something that is star-shaped, as in an astrocyte, a type of star-shaped cell in the brain and spinal cord.

Astro- comes from the Greek á���ٰ��Dz�, meaning “star.” The Greek á���ٰ��Dz� is also related to such words as asteroid and even the star itself. The word astronomy comes from a Greek word that literally (and poetically) means “star-arranging.”

What are variants of astro-?

When combined with words or word elements that begin with a vowel, astro- becomes astr-.

You have likely heard of the word (and even dreamed of becoming an) astronaut.

As we know, astro- means “star.” How about -naut? It ultimately comes from the Greek �Բ�ú��ŧ��, meaning “sailor.” Astronaut literally—and again, so poetically— translates to “star sailor.”

What are some other words that use the combining form astro-?

• astroarchaeology
• astroblastoma
• astrobleme
• astrobotany
• astrochemistry
• astrocompass
• astrocytoma
• astrodome
• astrodynamics
• astrology (via the equivalent form of astro- in Greek)
• astrogate
• astrogeology
• astroglia
• astrograph
• astrometry
• astrophysics

Learn about some other applications of astro- in our Vocab Builder article on Astroturf.

Similar to astro- are the combining forms cosmo- and cosm- (think cosmos). Learn more about these forms in our �������t¶��s That Use cosmo- and �������t¶��s That Use cosm- articles.

If navigating refers to moving ships in the water or planes in the sky, then what is astrogating?