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.

• (Received Pronunciation, General Australian) IPA^(key): /sɜːd/

  • Audio (Southern England):

    (file)

• (US) enPR: sûrd, IPA^(key): /sɝd/
• (Scotland) IPA^(key): /sʌɹd/
• (New Zealand) IPA^(key): /søːd/
• (Liverpool, fair–fur merger) IPA^(key): /seːd/
• (Humberside, Teesside, fair–fur merger) IPA^(key): /sɛːd/
• Rhymes: -ɜː(ɹ)d

surd (plural surds)

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

   Antonym: sonant

surd (comparative more surd, superlative most surd)

1. (obsolete) Lacking the sense of hearing; deaf.
   • 1670s, published 1716, Thomas Browne, Christian Morals, part 3, section 6:

     …how all Words fall to the Ground, spent upon such a surd and Earless Generation of Men, stupid unto all Instruction…

2. (obsolete) unheard
   • 1773, William Kenrick, A New Dictionary of the English Language, section 3, page 5:

     To this errour, of blending the ſurd and vocal modes of articulation together, may be added the too frequent uſe of compound articulations both vocal and ſurd.

3. (mathematics) Involving surds, or irrational numbers; not capable of being expressed in rational numbers.

   a surd expression or quantity; a surd number

4. (phonetics) unvoiced; voiceless

   Antonym: sonant

• absurd

• RUDs, Ruds, UDRS, Urds, ruds

• surdu, nsurdu

From Latin surdus. Compare Romanian surd.

surd m (feminine surde, plural surdz, feminine plural surdi)

1. deaf

• surdzest

Inherited from Latin surdus, from Proto-Indo-European *swer- (“ringing, whistling”). Compare Aromanian surdu.

• IPA^(key): /surd/

• Audio:

  (file)

• Audio:

  (file)

surd m or n (feminine singular surdă, masculine plural surzi, feminine and neuter plural surde)

1. deaf

• asurzi
• surditate
• surzi

• auzi
• mut
• orb