• In computers, a logic circuit which adds two or more numbers or quantities.
  • A circuit in which two or more input signals are combined to yield one output signal, which is proportional to the sum of the input signals.

Origin & History of “adder”

In Old English, the term for a snake (any snake, not just an adder) was nǣddre; there are or were related forms in many other European languages, such as Latin natrix, Welsh neidr, and German natter (but there does not seem to be any connection with the natterjack toad). around the 14th century, however, the word began to lose its initial consonant. The noun phrase including the indefinite article, a nadder, became misanalysed as an adder, and by the 17th century nadder had disappeared from the mainstream language (though it survived much longer in northern dialects).