periodical vs sporadic

periodical

adj
  • Periodic. 

  • Published at regular intervals of more than one day, especially weekly, monthly, or quarterly. 

  • Of, or relating to such a publication. 

noun
  • A regularly issued thematic publication that contains the most current information in its field, often the primary means for communication of original scholarship or creative work at the cutting edge of research in its field. 

  • A publication issued regularly, but less frequently than daily. 

sporadic

adj
  • Rare and scattered in occurrence. 

  • Exhibiting random behavior; patternless. 

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