verb

• (transitive) To connect or combine into one; to put together.
  "The plumber joined the two ends of the broken pipe."
• (intransitive) To come together; to meet.
  "Parallel lines never join."
• (intransitive) To enter into association or alliance, to unite in a common purpose.
  "Forſake thy king and do but ioyne with me And we will triumph ouer al the world."
• (transitive) To come into the company of.
  "I will join you watching the football game as soon as I have finished my work."

noun

• (computing, databases) An intersection of data in two or more database tables.
• (computing) The act of joining something, such as a network.
  "The offline domain join is a three-step process described subsequently: […]"
• (algebra) The lowest upper bound, an operation between pairs of elements in a lattice, denoted by the symbol ∨.