The suffix -ous (pronounced “us”) turns nouns into adjectives meaning “full of” or “having the quality of.” When you add -ous to a noun, you create a word that describes something possessing that quality.

Take danger: add -ous and you get dangerous, meaning full of danger. Poison becomes poisonous, meaning containing poison. Joy becomes joyous, meaning full of joy. The pattern works across hundreds of English words.

Sometimes the spelling changes slightly when adding -ous. Fury becomes furious, space becomes spacious, and mystery becomes mysterious. These spelling shifts follow patterns, but the meaning stays consistent: the adjective describes something that has the quality of the original noun.

You'll find -ous everywhere in English. A courageous person has courage. A mountainous region has mountains. A thunderous sound resembles thunder. The suffix creates precise, powerful adjectives that pack meaning into a single word.

When you recognize -ous at the end of a word, you've found a clue to its meaning. Even if you encounter an unfamiliar word like magnanimous or vociferous, knowing that -ous means “full of” can help you start figuring out what the word means.