noun (1)
ad·​der | \ ˈa-dər \

Definition of adder

 (Entry 1 of 2)

1 : the common venomous viper (Vipera berus) of Europe broadly : any of various snakes of the viper family — compare puff adder
2 : any of several North American snakes (such as the hognose snakes) that are harmless but are popularly believed to be venomous


noun (2)
add·​er | \ ˈa-dər \

Definition of adder (Entry 2 of 2)

: one that adds especially : a device (as in a computer) that performs addition

Illustration of adder

Illustration of adder

Noun (1)

adder 1

In the meaning defined above

How Adder Lost Its First Letter

Words formed by what linguists call “false division,” “misdivision,” or “metanalysis” have spellings that record a mistake that was made at some point in their history, when the spelling or sound of the word was split in the wrong place.

Misdivisions of words that begin with the letter n are frequent because, in speech, it is difficult to distinguish between the sound of the indefinite article “a” followed by a word beginning with an n (as in “a name”) and the sound of the indefinite article “an” followed by a word beginning with a vowel (as in “an aim”). This make the position of the n very easily confused.

An example is the name of the venomous snake known as the adder. The Old English word for this viper was nǣdre, which became nadder in Middle English. Over time, a nadder became an adder. By by the mid-1400s, the word was being spelled both with and without the n, but since about 1500, the n-less spelling has prevailed.

First Known Use of adder

Noun (1)

14th century, in the meaning defined at sense 1

Noun (2)

1547, in the meaning defined above

History and Etymology for adder

Noun (1)

Middle English addre, eddre, alteration (resulting from misdivision of a naddre) of naddre, neddre, going back to Old English nǣdre "adder, snake," going back to West Germanic nēdrōn- (whence also Old Saxon nādra "grass snake [Natrix natrix or allied species]," Old High German nātara, nāter), going back to dialectal (western) Indo-European *neh1tr-, full-grade ablaut of *nh1tr- (whence Old Norse naðr "adder, snake," Gothic nadrs "snake, viper," Latin natric-, natrix "water snake [as Natrix maura]," Old Irish nathir [genitive singular nathrach] "snake," Welsh neidr [plural nadredd], Breton aer, naer "grass snake"), perhaps from *(s)neh1- "twist together, spin" + *-tr-, -ter-, agent suffix (hence "one who winds, twists") — more at needle entry 1

Noun (2)

add + -er entry 2

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Time Traveler for adder

The first known use of adder was in the 14th century

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More Definitions for adder


ad·​der | \ ˈa-dər \

Kids Definition of adder

1 : a poisonous snake of Europe or Africa
2 : a harmless North American snake


ad·​der | \ ˈad-ər \

Medical Definition of adder

1 : the common venomous European viper of the genus Vipera (V. berus) broadly : a terrestrial viper of the family Viperidae
2 : any of several North American snakes (as the hognose snakes) that are harmless but are popularly believed to be venomous

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More from Merriam-Webster on adder

Rhyming Dictionary: Words that rhyme with adder

Spanish Central: Translation of adder

Nglish: Translation of adder for Spanish Speakers

Britannica English: Translation of adder for Arabic Speakers Encyclopedia article about adder

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