Definition

1. Adjective:

   • In phonetics: Describes a speech sound produced without vibration of the vocal cords; voiceless.
   • In mathematics (archaic): Irrational (as in a number that cannot be expressed as a simple fraction).

2. Noun:

   • In phonetics: A consonant sound produced without vibration of the vocal cords; a voiceless consonant.
   • In mathematics (archaic): An irrational number or quantity, especially an irrational root.

Usage and Examples

• Adjective (Phonetics):
  • The sounds /p/, /t/, and /k/ are surd consonants.
  • In English, surd sounds like /s/ and /ʃ/ are common.
• Adjective (Mathematics):
  • The term surd is rarely used in modern mathematics, having been largely replaced by "irrational".
• Noun (Phonetics):
  • Linguists classify /f/ as a surd.
  • The word "stop" begins with the surd /s/.
• Noun (Mathematics):
  • The square root of 2 is a classic example of a surd.

Advanced Usage and Notes

• The primary contemporary use of surd is in the field of phonetics and linguistics. Its mathematical usage is considered archaic.
• In phonetics, surd is synonymous with "voiceless" and is the direct opposite of "sonant" (voiced).
• The term can be used descriptively in grammar or pronunciation guides: "The final consonant in 'cats' is a surd."

Variants and Related Words

• Voiceless (adj/n): The modern, more common synonym for surd in phonetics.
• Sonant (adj/n): The antonym, describing a voiced sound produced with vocal cord vibration.
• Irrational (adj/n): The modern term for the mathematical concept of a surd number.

Synonyms

• Adjective/Noun (Phonetics): Voiceless, unvoiced.
• Adjective/Noun (Mathematics): Irrational (archaic context).

Antonyms

• Adjective/Noun (Phonetics): Voiced, sonant.
• Adjective/Noun (Mathematics): Rational.

Related Phrases and Concepts

• Surd consonant: A standard phrase in phonetics to specify a voiceless consonant sound.
• Surd and sonant: A traditional paired classification for speech sounds based on the presence or absence of voicing.

Adjective

1. produced without vibration of the vocal cords
   • unvoiced consonants such as `p' and `k' and `s'

Noun

1. a consonant produced without sound from the vocal cords