What is the meaning of central?

noun

• A workplace that serves as a telecommunications facility where lines from telephones can be connected together to permit communication.
  • synonyms: telephone exchange, exchange

adjective

• Serving as an essential component.
  • usage: "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure"
  • synonyms: cardinal, fundamental, key, primal
• In or near a center or constituting a center; the inner area.
  • usage: "a central position"