an vs per

an

prep
  • In each; to or for each; per. 

noun
  • The first letter of the Georgian alphabet, ა (Mkhedruli), Ⴀ (Asomtavruli) or ⴀ (Nuskhuri). 

num
  • one 

article
  • Used before one and words with initial u, eu. 

  • Used before a vowel sound. 

  • Used before all consonants. 

  • Used before /h/ in an unstressed syllable. 

  • Used before /h/ in a stressed syllable. 

per

prep
  • For each. 

  • In accordance with, as per 

  • By the, by means of the, via the, through the. 

  • To each, in each (used in expressing ratios of units). 

adj
  • Belonging to per, their (singular). Gender-neutral third-person singular possessive adjective, coordinate with gendered his and her. 

pron
  • They (singular). Gender-neutral neologistic third-person singular subject pronoun, coordinate with gendered pronouns he and she. 

  • Them (singular) Neologistic gender-neutral third-person singular object pronoun, suggested for use in place of him and her. 

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