O, Oh

Both O and Oh are relatively rare in everyday writing, but may appear in titles or dialogue.

Capitalize O when formally addressing a person or thing. No punctuation is needed with O.

  • The students sing “O Canada” as loudly as possible every morning.
  • “O wild West Wind, thou breath of Autumn’s being …” is the opening line of Shelley’s “Ode to the West Wind.”

The interjection or exclamation Oh is followed by a comma, exclamation mark or em–dash.

  • Oh, no! I’ve dropped my keys down the elevator shaft.
  • Oh! The northern lights are amazing tonight!
  • Oh—are you really going to Nunavut for your summer holiday?

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