join vs sign on

join

verb
  • To become a member of. 

  • To unite in marriage. 

  • To produce an intersection of data in two or more database tables. 

  • To come into the company of. 

  • To come together; to meet. 

  • To accept, or engage in, as a contest. 

  • To connect or combine into one; to put together. 

  • To enter into association or alliance, to unite in a common purpose. 

noun
  • An intersection of data in two or more database tables. 

  • The act of joining something, such as a network. 

  • The lowest upper bound, an operation between pairs of elements in a lattice, denoted by the symbol ∨. 

  • An intersection of piping or wiring; an interconnect. 

sign on

verb
  • To join something, after signing. 

  • To begin broadcasting a radio or television signal, usually at the beginning of a broadcasting day and after being off the air for several hours. 

  • To commit oneself, as to a project, a goal, an organization, a cause. 

  • To apply to receive unemployment benefits. 

  • To log on; to start using a computer, radio, etc., or to start talking. 

noun
  • The time of day when a radio or television station begins broadcasting, usually after being off the air for several hours. 

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