exo-

exo- — combining form

1. a prefix borrowed from Greek that means 'outside,' 'external,' or 'on the outer

1.構詞成分B2
釋義

a prefix borrowed from Greek that means 'outside,' 'external,' or 'on the outer side of something'; used in scientific and technical words to describe things that exist or happen beyond a boundary, surface, or system.

例句

Many insects have a hard outer covering called an exoskeleton that protects their body.

exoskeleton = exo- + skeleton (hard outer shell)

Astronomers recently discovered a new exoplanet orbiting a star thirty light-years away.

exoplanet = exo- + planet (planet outside our solar system)

同義詞
  • extra-

    also means 'outside' or 'beyond,' but extra- is more common in everyday words (extraordinary, extracurricular); exo- is chiefly scientific.

  • out-

    an English-origin prefix (outdoor, outflow); exo- comes from Greek and is used in formal/technical terms.

反義詞
  • endo-

    means 'inside' or 'within' (endoskeleton, endothermic); the direct opposite of exo- in scientific contexts.

  • in-

    a Latin prefix meaning 'in' or 'into' (inhale, inside); less technical than endo- but also contrasts with exo-.

文法句型

exo- + [noun] forms a noun

exo- + [adjective] forms an adjective

用法筆記

Frequently used in scientific and technical vocabulary, especially biology, astronomy, and chemistry. Contrast with the prefix 'endo-' (inside, internal): exoskeleton vs. endoskeleton, exothermic vs. endothermic.

常見錯誤

❌The insect has an exterior skeleton.
✅The insect has an exoskeleton.
💡The standard technical term is exoskeleton, not 'exterior skeleton.'
❌An exoplanet is a planet outside the solar system.
✅An exoplanet is a planet that orbits a star outside our solar system.
💡The prefix exo- specifically means 'outside' the system in question, not just 'exterior.'

2. a prefix meaning 'outward,' 'away from,' or 'turning out' — used in social scien

2.構詞成分C1
釋義

a prefix meaning 'outward,' 'away from,' or 'turning out' — used in social sciences and biology to describe movement away from a group, place, or system.

例句

The Book of Exodus describes the departure of the Israelites from Egypt.

exodus = exo- + (h)odos 'way' (a mass departure outward)

Exogamy is the custom of marrying someone from outside one's own tribe or community.

exogamy = exo- + gamy 'marriage' (marrying outside the group)

同義詞
  • outward

    full word, not a prefix; less precise than exo- for technical contexts.

反義詞
  • endo-

    in its sense meaning 'within the group' — endogamy is marriage within one's own group, the opposite of exogamy.

文法句型

exo- + [noun] forms a noun

用法筆記

Less common than sense 1 ('outside'). Most words with this sense are specialized terms from anthropology, sociology, biology, or linguistics. The noun 'exodus' is by far the most widely used word in this group.

常見錯誤

❌They planned an exo to the countryside.
✅They planned an exodus to the countryside.
💡'Exodus' is the noun form; 'exo' alone is not a word in English.

❌ 'An exogamous marriage is one that happens outside the family group.' (this is correct but the word 'exogamy' is rare) — Use 'exogamy' only in formal or academic writing about marriage systems.