Definition of "OH"

(US) Abbreviation of Ohio.  examples

(Internet slang) Initialism of other half: a husband, wife, partner, etc.

(US, army, aviation) Initialism of observation helicopter.  examples

Initialism of office hours.  examples

(organic chemistry) A hydroxyl, or alcohol, functional group.  examples

(inorganic chemistry) A hydroxide radical, or hydroxyl group.  examples