# mammal

/ˈmæməɫ/ (US) · /mˈæməl/ (UK)

Source: https://englishreference.com/word/mammal
Updated: 2026-08-27

## Senses

### 1. biological category

noun · CEFR B1

a warm-blooded animal that has hair or fur and feeds its babies with milk from the mother.

For teachers: a vertebrate animal of the class Mammalia, characterized by endothermic regulation, the presence of hair or fur, and mammary glands in females.

- Whales are actually mammals, not fish, because they breathe air and give birth to live young.
- Biologists classify humans, dogs, and even dolphins as mammals due to their shared physiological traits and reproductive methods.

### 2. anatomical definition

noun · CEFR C2 · Technical

an animal with a specific bone structure, including three small bones in the ear.

For teachers: a vertebrate distinguished by specific skeletal features, including three middle-ear ossicles and a single bone in the lower jaw.

- Scientists can identify an ancient fossil as a mammal by looking at the shape of its jaw.
- The transition from reptilian ancestors is marked by the migration of jaw bones to the inner ear, a defining characteristic of the modern mammal.

## Examples

- A whale is a mammal that lives in the ocean.
- While most animals lay eggs, almost every mammal gives birth to live young and cares for them during infancy.
- The platypus is a unique mammal because it lays eggs yet still possesses mammary glands to provide milk for its hatchlings.

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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.