mortal vs perennial

mortal

adj
  • Human; belonging or pertaining to people who are mortal. 

  • Of or relating to the time of death. 

  • Punishable by death. 

  • Affecting as if with power to kill; deathly. 

  • Very painful or tedious; wearisome. 

  • Susceptible to death by aging, sickness, injury, or wound; not immortal. 

  • Causing death; deadly, fatal, killing, lethal (now only of wounds, injuries etc.). 

  • Of a sin: involving the penalty of spiritual death, rather than merely venial. 

  • Very drunk. 

  • Fatally vulnerable. 

adv
  • Mortally; enough to cause death. 

noun
  • A human; someone susceptible to death. 

perennial

adj
  • Lasting or remaining active throughout the year, or all the time. 

  • Appearing or recurring again and again; recurrent. 

  • Continuing without cessation or intermission for several years, or for an undetermined or infinite period; neverending or never failing; perpetual, unceasing. 

  • Of a plant: active throughout the year, or having a life cycle of more than two growing seasons. 

  • Appearing again each year; annual. 

noun
  • A plant that is active throughout the year, or has a life cycle of more than two growing seasons. 

  • A thing that lasts forever. 

  • A person or thing (such as a problem) that appears or returns regularly. 

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