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surd

Pronunciation: /sɜːd/

The English word “surd” has 6 meanings listed here.

noun

  1. An irrational number, especially one expressed using the √ symbol.
  2. A voiceless consonant.

adjective

  1. Lacking the sense of hearing; deaf.
  2. unheard
  3. Involving surds, or irrational numbers; not capable of being expressed in rational numbers.
  4. unvoiced; voiceless

Etymology

First attested in the mid 16th century from Latin surdus (“deaf, mute”), used in mathematics for “irrational,” reflecting ἄλογος (álogos, “irrational, speechless”) as found in Euclid, apparently transmitted via Arabic جِذْر أَصَمّ (jiḏr ʔaṣamm, “deaf root”). The phonetic sense, “voiceless,” emerged in the 18th century. Doublet of surdo.

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Definitions are from Wiktionary, extracted by Kaikki.org, and are available under the CC BY-SA 4.0 licence.