initial vs prior

initial

adj
  • Chronologically first, early; of or pertaining to the beginning, cause or origin. 

  • Spatially first, placed at the beginning, in the first position; especially said of the first letter of a word. 

noun
  • A distinguished initial letter of a chapter or section of a document. 

  • onset, part of a syllable that precedes the syllable nucleus in phonetics and phonology. 

  • The first letter of a word or a name. 

  • In plural, the first letter of each word of a person's full name considered as a unit. 

verb
  • To sign one's initial(s), as an abbreviated signature. 

prior

adj
  • Advance; previous; coming before. 

  • Former, previous. 

adv
  • Previously. 

noun
  • A high-ranking member of a monastery, usually lower in rank than an abbot. 

  • A prior probability distribution, one based on information or belief before additional data is collected. 

  • A belief supported by previous evidence or experience that one can use to make inferences about the future. 

  • A chief magistrate in Italy. 

  • A previous arrest or criminal conviction on someone's record. 

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