SINCE 1828

An Encyclopædia Britannica Company

oxygen cycle

noun

Definition of oxygen cycle

: the cycle whereby atmospheric oxygen is converted to carbon dioxide in animal respiration and regenerated by green plants in photosynthesis

First Known Use of oxygen cycle

1935

Learn More about oxygen cycle

Britannica.com: Encyclopedia article about oxygen cycle

Seen and Heard

What made you want to look up oxygen cycle? Please tell us where you read or heard it (including the quote, if possible).

show

WORD OF THE DAY

flagrant

play

conspicuously offensive

Words at Play

alt-599ca1388698f

Drawing a Conclusion About "Sketchy"

How did "sketchy" come to describe creeps?

2-pairs-of-scissors

What's the Singular of 'Scissors'?

A tricky, double-edged word origin.

a-woman-waits-at-the-end-of-a-gloomy-pier-does-she-wait-for-charon-the-ferryman-to-the-underworld-it-is-dark-but-she-carries-a-parasol

Great Words for Twilight and Darkness

Words for the goth in all of us

bunch-of-yellow-balloons-lit-by-the-sun

Helium: This Word Brought to You by a Solar Eclipse

And by the Sun, with some help from Greek.

Ask the Editors

video-title-words-of-the-year-1066

Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless

Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals

Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

time-traveler-quiz-which-word-came-first

Time Traveler Quiz: Which Word Came First?

Which word entered the English language first?

Take the quiz

Name More Food!

Test your knowledge of food vocabulary!

Take the quiz

Spell It

Can you spell these 10 commonly misspelled words?

Take the quiz

Word Winder's CrossWinder

Word Winder's CrossWinder

A game of winding words.

Play the game