first vs posterior

first

adj
  • Preceding all others of a series or kind; the ordinal of one; earliest. 

  • Of or belonging to a first family. 

  • Most eminent or exalted; most excellent; chief; highest. 

adv
  • For the first time. 

  • Before anything else; firstly. 

  • Now. 

noun
  • first base 

  • A first-edition copy of some publication. 

  • A fraction whose (integer) denominator ends in the digit 1. 

  • The first gear of an engine. 

  • Something that has never happened before; a new occurrence. 

  • A first-class honours degree. 

  • The person or thing in the first position. 

posterior

adj
  • Following in order or in time. 

  • Next to, or facing the main stem or axis. 

  • Relating to or denoting presentation of a fetus in which the rear or caudal end is nearest the cervix and emerges first at birth. 

noun
  • The hinder parts of the body. 

  • The probability that a hypothesis is true (calculated by Bayes' theorem). 

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