noun
adder
AD
noun
1
A small venomous snake found across Europe, including Britain, marked with a dark zigzag pattern down its back.
"She spotted an adder basking on the warm rocks."
"The adder is the only venomous snake native to the UK."
2
A person or device that performs addition.
"The circuit uses a binary adder to combine the two signals."
"An old mechanical adder sat on the accountant's desk."
How to Use Adder
Learner’s notesIn plain EnglishEither a venomous European snake, or something (a person or machine) that adds numbers.
Memory tip
The word split from "nadder" by a mishearing of the article — a quirky bit of English history worth remembering.
Trace the full origin ↓
Common pairings
a venomous adder
binary adder
Word Forms
adders plural, adders plural, ADDers plural
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She spotted an _____ basking on the warm rocks.
Etymology
From Middle English naddere. The "n" was lost when "a naddere" was misheard as "an addere" — the same shift that turned "a napron" into "an apron."