- (US) Ohio, a state of the United States of America.
- (organic chemistry) Symbol for a hydroxyl, or alcohol, functional group.
- (inorganic chemistry) Symbol for a hydroxide radical, or hydroxyl group.
- (US, army, aviation) Prefix code for observation helicopter designations.
- (Internet slang) Other half, i.e., husband, wife, partner, etc.
- Initialism of office hours..