# adder

/ˈædɝ/ (US) · /ˈædɐ/ (UK)

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

## Senses

### 1. a snake

noun · CEFR B2 · British English

a small poisonous snake, often with a dark zigzag pattern on its back.

For teachers: the common European viper (Vipera berus), noted for being the only venomous snake native to Britain.

- We saw a small adder sunning itself on a rock during our hike.
- The adder is generally shy and will only strike if it feels cornered or is accidentally stepped on by a hiker.

Usage: In North America, the term is sometimes applied to other non-venomous snakes like the milk snake.

### 2. math/computing

noun · CEFR C1 · Technical

a person who adds numbers, or a machine or computer part that does addition.

For teachers: a person who performs arithmetic addition, or a digital circuit that calculates the sum of numbers.

- The computer uses a high-speed adder to process the math problems.
- A full adder is a fundamental component of a central processing unit, capable of handling carry bits from previous operations.

### 3. person with ADD

noun · CEFR C2 · Informal · Slang

a person who has attention deficit disorder (ADD).

For teachers: a person diagnosed with or exhibiting symptoms of attention deficit disorder.

- As an adder, he finds it helpful to use a timer to stay focused on his work.
- The support group provides a space for adders to share strategies for managing executive dysfunction in a professional environment.

Teaching tip: This is a niche slang term derived from the acronym ADD; it is not a standard medical term and may be confusing to those unfamiliar with neurodiversity slang.

## Examples

- The hiker saw an adder resting in the grass.
- While walking through the meadow, we were warned to watch for the local adder population.
- The European adder is one of the few venomous snakes found in the British Isles, though its bite is rarely fatal to healthy adults despite the potent neurotoxins it produces.

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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.