1. Symbol for oxygen; orotidine.
2. In chemistry, the abbreviation for ortho-.
3. Symbol for a blood group in the ABO system. See ABO blood group, Blood Groups appendix.
4. An abbreviation derived from ohne Hauch (without a film), used as a designation for: 1) antigens that occur in the bacterial cell, in contrast to those in the flagella; 2) specific antibodies for such somatic antigens; 3) the agglutinative reaction between somatic antigen and its antibody.
(05 Mar 2000)