Words ending in -ious and -eous

Both of these endings are used to form adjectives (e.g. cautious or hideous). Words ending with -ious are far more common than those ending in -eous, but unfortunately there are no set rules which can help you choose the correct one.

Here are some common adjectives ending in -ious:

ambitious; previous; curious; anxious; delicious; rebellious; religious; serious; envious; superstitious; notorious; glorious; conscious; various; hilarious; ferocious; obvious;  studious; tedious; victorious.

And here are some of the most important ones that end in -eous:

gorgeous; curvaceous; nauseous; courteous; erroneous; courteous; plenteous; simultaneous; miscellaneous; spontaneous; gaseous.

There is also a small group of adjectives that take the spelling -eous when the ending -ous is added. This is because the word they are formed from ends in -ge and keeps the final -eso as to be pronounced with a soft ‘ge’ sound. The most important of these are:

  • advantageous, from advantage
  • courageous, from courage
  • outrageous, from outrage

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Grammar and usage