I. interjection
also O (ˈ)ō
Etymology: Middle English o
Date: 13th century
1. — used to express an emotion (as surprise or desire) or in response to physical stimuli
2. — used in direct address
oh , waiter! Will you come here, please?
3. — used to express acknowledgment or understanding of a statement
4. — used to introduce an example or approximation
II. ˈō noun
Etymology: o; from the similarity of the symbol for zero (0) to the letter O
Date: 1936
: zero