O

O

O¹ [ō]

n.

pl. O's

1. popularly the figure zero; nought: in printed matter, zero is usually differentiated from the letter O, as in this dictionary: “O” is the character used for the letter, “0” is the character used for the number

2. a blood type: see ABO SYSTEM

O² [ō]

interj.

1. used in direct address [O Lord!]

2. used to express surprise, wonder, fear, pain, etc.: now usually oh

3. used at the end of a line in some ballads

n.

pl. O's

an instance of this exclamation: O and oh are now often interchangeable

O³

abbrev.

1. Ocean

2. October

3. Ohio

4. Physics ohm

5. Linguis. Old [OFr]

6. Ontario

7. Baseball out(s)out(s)

8. [L octarius] Pharmacy pint

O⁴

Chem.

symbol

oxygen