Meaning

• To happen or take place.

  "The liftoff will occur in exactly twelve seconds."

• To present or offer itself.

  "I will write if the opportunity occurs."

• To come or be presented to the mind; to suggest itself.

• To be present or found.

  "The chemical monofluoroacetate occurs in all parts of Dichapetalum cymosum, and is responsible for its toxic effects."