hexad vs sixth

hexad

noun
  • A group of six. 

  • An element or radical with the combining power of six units, i.e. six atoms of hydrogen. 

sixth

noun
  • One of six equal parts of a whole. 

  • The interval between one note and another, five notes higher in the scale, for example C to A, a major sixth, or C to A flat, a minor sixth. (Note that the interval covers six notes counting inclusively, for example C-D-E-F-G-A.) 

  • The person or thing in the sixth position. 

verb
  • to divide by six, which also means multiplying a denominator by six 

adj
  • The ordinal form of the number six. 

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