membership vs rivalry

membership

noun
  • The state of being a member of a group or organization. 

  • The body of members of an organization. 

  • The fact of being a member of a set. 

rivalry

noun
  • The characteristic of being a rivalrous good, such that it can be consumed or used by only one person at a time. 

  • An ongoing relationship between (usually two) rivals who compete for superiority. 

  • Any competition between two or more things or factors. 

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