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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A tool created and made available online by the Translation Bureau, Public Services and Procurement Canada
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