continuous vs periodical

continuous

adj
  • Without stopping; without a break, cessation, or interruption. 

  • Expressing an ongoing action or state. 

  • Not deviating or varying from uniformity; not interrupted; not joined or articulated. 

  • Such that, for every x in the domain, for each small open interval D about f(x), there's an interval containing x whose image is in D. 

  • Without intervening space; continued. 

  • Such that each open set in the target space has an open preimage (in the domain space, with respect to the given function). 

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. 

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