surd vs vocal

surd

noun
  • A voiceless consonant. 

  • An irrational number, especially one expressed using the √ symbol. 

adj
  • unvoiced; voiceless 

  • Involving surds, or irrational numbers; not capable of being expressed in rational numbers. 

vocal

noun
  • A vocal sound; specifically, a purely vocal element of speech, unmodified except by resonance; a vowel or a diphthong; a tonic element; a tonic. 

  • A part of a piece of music that is sung. 

  • A musical performance involving singing. 

  • A man in the Roman Catholic Church who has a right to vote in certain elections. 

adj
  • Relating to, composed or arranged for, or sung by the human voice. 

  • Of, pertaining to, or resembling the human voice or speech. 

  • Consisting of, or characterized by, voice, or tone produced in the larynx, which may be modified, either by resonance, as in the case of the vowels, or by obstructive action, as in certain consonants, such as v, l, etc., or by both, as in the nasals m, n, ng. 

  • Used in the production of speech sounds. 

  • Synonym of expressive. 

  • Uttered or modulated by the voice; expressed in words. 

  • Full of voices. 

  • Expressing opinions or feelings freely, loudly, or insistently. 

  • Having or exercising the power of producing voice, speech, or sound. 

  • Synonym of vocalic. 

How often have the words surd and vocal occurred in a corpus of books? (source: Google Ngram Viewer )