1. A classification system for the antigens of human blood; used in blood transfusion therapy; four groups are A and B and AB and O
   - ABO blood group system, ABO system

Type of: classification system

• face-saving
• faced
• faceless
• facelift
• faceplate
• facer
• facet
• facet plane
• faceted
• facetiae
• facetious
• facetiously
• facetiousness
• facia
• facial
• facial artery
• facial expression
• facial gesture
• facial hair
• facial index
• facial muscle
• facial nerve
• facial profiling
• facial recognition
• facial tissue