irregularity vs roughness

irregularity

noun
  • An object or event that is not regular or ordinary. 

  • A violation of rules. 

  • An instance of being irregular. 

  • Irregular bowel movement (e.g. diarrhea or constipation). 

  • The state or condition of being irregular, or the extent to which something is irregular. 

roughness

noun
  • Something that is rough; a rough spot. 

  • A measure of how rough something is, such as a surface 

  • Abundance, especially of food. 

  • Roughage; coarse fodder. 

  • The property of being rough, coarseness. 

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