# gill

/ˈɡɪɫ/ (US) · CEFR B2 · Noun

Source: https://englishreference.com/word/gill
Updated: 2026-08-15

## Definition

the part of a fish's body that it uses to breathe underwater. It takes oxygen out of the water and lets the fish live without air.

For teachers: the respiratory organ of aquatic animals, such as fish and amphibians, that extracts dissolved oxygen from water. Typically located on the sides of the head and protected by a bony cover.

## Examples

- The fish moved its gills to breathe in the tank.
- As the shark swims forward, water passes over its gills to provide the oxygen needed for its muscles.
- Unlike mammals that rely on lungs, most teleost fish utilize a counter-current exchange system within their gills to maximize the efficiency of gas exchange from the surrounding water.

## Usage notes

- Usually used in the plural ('gills') when referring to the respiratory system as a whole.

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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.