Definitions of happen:

• verb:   chance to be or do something, without intention or causation

  Example: "I happen to have just what you need!"

• verb:   come to pass

  Example: "What is happening?"

• verb:   come into being; become reality
• verb:   happen, occur, or be the case in the course of events or by chance

  Example: "It happens that today is my birthday"

• verb:   come upon, as if by accident; meet with

  Example: "I happened upon the most wonderful bakery not very far from here"