pluriennial vs yearlong

pluriennial

adj

  • Lasting a few years 

yearlong

adj

  • Lasting one year; of a timespan of one year. 

  • Which lasts throughout every year; which is not seasonal 

adv

  • Throughout every year; not seasonally 

  • Per year. 

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