Phonetics. voiceless (opposed to sonant).
Mathematics. (of a quantity) not capable of being expressed in rational numbers; irrational.


Phonetics. a voiceless consonant (opposed to sonant).
Mathematics. a surd quantity.

Origin of surd

First recorded in 1545–55, surd is from the Latin word surdus dull-sounding, mute, deaf Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for surd

dumb, inarticulate, mum, mute, silent, speechless, aphonic

Examples from the Web for surd

Historical Examples of surd

British Dictionary definitions for surd



maths an expression containing one or more irrational roots of numbers, such as 2√3 + 3√2 + 6
phonetics a voiceless consonant, such as (t)


of or relating to a surd

Word Origin for surd

C16: from Latin surdus muffled
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for surd

1550s, "irrational" (of numbers), from Latin surdus "unheard, silent, dull," possibly related to susurrus "a muttering, whispering" (see susurration). The mathematical sense is from the use of Latin surdus to translate Arabic (jadhr) asamm "deaf (root)," itself a loan-translation of Greek alogos, literally "speechless, without reason" (Euclid book x, Def.). In French, sourd remains the principal word for "deaf."

Online Etymology Dictionary, © 2010 Douglas Harper