Prefix · position · outside
Means "outside" or "external": exotic, exoskeleton, exoplanet, exodus, exosphere.
Written by Bryan López, English teacher · Updated
Exo- comes from the Greek exo, which means "outside" or "external". It shows that something is outside a limit or comes from the outside. Almost all its words are scientific. It is the opposite of endo-, which means "inside".
Even though they sound alike, they are not the same. Exo- talks about an outside position that stays still: something that is outside. Ex- talks about origin or movement: something that goes out or is taken out. In practice, exo- shows up almost only in scientific vocabulary, while ex- is used in everyday English.
Attaches to scientific nouns to indicate exterior position:
Pronunciation: /ˈeksəʊ/. Do not confuse with ex- (Latin, movement/former): export, exclude, ex-president. Exo- is Greek and describes exterior position; ex- is Latin and describes outward movement or former status.
exo-/ˈeksəʊ/
Tap the button to hear how the prefix sounds. Each word in the table has its own audio.
"Exo-" (Greek "exo"): static exterior position. "Ex-" (Latin "ex"): outward movement or former status. Exoskeleton = skeleton positioned on the outside. Export = move goods out. Ex-president = former president. Different roots, different uses — though both relate to "outside" in a broad sense.
A trick to remember it
Picture a shell worn on the outside of the body: exo- = external. exoskeleton, exoplanet.
Exercise 1 · Form the word
Exercise 2 · Pick the right one
What is the difference between "exo-" and "ex-"?
The prefix exo- means "outside" or "external": exotic, exoskeleton, exoplanet, exodus, exosphere.
The prefix exo- is pronounced /ˈeksəʊ/. For example, "exotic".
"tic" becomes "exotic". It is a typical example of the exo- prefix.
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