Prefix · stars / space
Signals relation to stars or outer space: astronaut, astronomy, astrophysics, asteroid.
Written by Bryan López, English teacher · Updated
Astro- comes from Greek "astron" (star) and signals a relation to stars, space, or celestial bodies: astronomy = the study of stars and the universe; astronaut = one who "sails" among the stars (nautes = sailor in Greek); astrology = the study of the (supposed) influence of stars on people; asteroid = a rocky body with a star-like appearance.
In modern science, astro- is widely used: astrophysics = the physics of celestial objects; astrobiology = the study of possible life in the universe; astrochemistry = the chemistry of molecules in space. It also appears in technical words like astrodynamics (orbital mechanics) and astronavigation (celestial navigation).
Attaches to scientific nouns. Identical in Spanish and English:
Pronunciation: /ˈæstrəʊ/. Identical in Spanish and English.
astro-/ˈæstrəʊ/
Tap the button to hear how the prefix sounds. Each word in the table has its own audio.
"Astronomy" is a rigorous science studying celestial bodies with empirical methods. "Astrology" is a belief system claiming that the positions of stars affect human personality and fate. The scientific community does not recognise astrology as a science.
"Astronaut" combines "astron" (star) with "nautes" (sailor, navigator). The same root "-naut" appears in "cosmonaut" (Russian/Soviet term for space sailor) and "taikonaut" (the term for Chinese astronauts).
A trick to remember it
Astro- = "star" or "space": astronaut = a sailor through space, astronomy = the science of stars, astrophysics = the physics of the universe. Identical in Spanish and English. Do not confuse astronomy (science) with astrology (a belief system without scientific support).
Exercise 1 · Form the word
Exercise 2 · Pick the right one
"An ___ is a rocky body orbiting the sun, smaller than a planet but larger than a meteoroid."
Exercise 3 · Pick the right one
What is the key difference between "astronomy" and "astrology"?
The prefix astro- signals relation to stars or outer space: astronaut, astronomy, astrophysics, asteroid. In Spanish it usually maps to astro-.
The prefix astro- is pronounced /ˈæstrəʊ/. For example, "astronaut".
"naut" becomes "astronaut". It is a typical example of the astro- prefix.
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