# oxygen

/ˈɑksədʒən/ (US) · /ˈɒksɪdʒən/ (UK)

Source: https://englishreference.com/word/oxygen
Updated: 2026-06-19

## Senses

### 1. the gas we breathe

noun · CEFR B1

the gas in the air that you need to breathe to stay alive.

For teachers: the molecular form of the element (O₂) which constitutes approximately 21 percent of the Earth's atmosphere and is vital for life.

- The doctor gave the patient some oxygen to help him breathe more easily.
- Plants produce oxygen during photosynthesis, which is then released into the atmosphere and used by animals for cellular respiration.

Usage: Uncountable when referring to the gas in general; countable only in technical chemical contexts referring to specific atoms.

### 2. the chemical element

noun · CEFR B2 · Technical

the chemical element with the symbol O and atomic number 8.

For teachers: the chemical element with atomic number 8; it is the most abundant element by mass in the Earth's crust.

- Water is made of two parts hydrogen and one part oxygen.
- The researcher analyzed the isotopes of oxygen found within the ice core samples to determine historical temperature fluctuations.

### 3. support for an idea

noun · CEFR C1 · Literary

the things or attention that an idea or project needs to grow and succeed.

For teachers: the metaphorical 'air' or support required for an idea, movement, or person to flourish or remain relevant.

- The new law gave the small business community the oxygen it needed to grow.
- By refusing to debate the extremist group, the prime minister denied them the oxygen of publicity they so desperately craved.

## Examples

- Humans need oxygen to survive.
- The hospital patient was given extra oxygen through a mask to help him breathe more easily during recovery.
- Deep-sea divers must carefully monitor their oxygen levels to prevent toxicity, as the partial pressure of gases increases significantly at greater depths.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.