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Added 9 October 2026

surd

/sɜːd/ noun

Latin root: surdus First recorded: mid 16th century Wiktionary

noun Definition from Wiktionary (CC BY-SA). Pronunciation from Wiktionary, via Kaikki.org. More about surd at Wordnik → Where our words come from →

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

adjective

Lacking the sense of hearing; deaf.
Involving surds, or irrational numbers; not capable of being expressed in rational numbers.
a surd expression or quantity; a surd number
unvoiced; voiceless

Origin

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.

From Wiktionary, via Kaikki.org (CC BY-SA)

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