oral vs surd

oral

adj
  • Spoken rather than written. 

  • Pronounced by the voice resonating in the mouth, as the vowels in English. 

  • Done or taken by the mouth. 

  • Relating to or denoting a stage of infantile psychosexual development during which libidinal gratification is derived from intake (as of food), by sucking, and later by biting. 

  • Relating to the transmission of information or literature by word of mouth. 

  • Of, relating to, or characterized by personality traits of passive dependency and aggressiveness. 

  • Relating to the mouth. 

  • Using speech or the lips especially in teaching the deaf. 

  • Not having reached the stage of literacy. 

noun
  • A physical examination of the mouth. 

  • A spoken test or examination, particularly in a language class. 

surd

adj
  • unvoiced; voiceless 

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

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

  • A voiceless consonant. 

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