- AB, type AB, group AB - the blood group whose red cells carry both the A and B antigens
--1 is a kind of blood group, blood type
- Bachelor of Arts, BA, Artium Baccalaurens, AB - a bachelor's degree in arts and sciences
--2 is a kind of bachelor's degree, baccalaureate
- Ab, Av - the eleventh month of the civil year; the fifth month of the ecclesiastical year in the Jewish calendar (in July and August)
--3 is a kind of Jewish calendar month
--3 is a part of Jewish calendar, Hebrew calendar - abdominal, abdominal muscle, ab - the muscles of the abdomen
--4 is a kind of skeletal muscle, striated muscle
--4 is a part of abdomen, venter, stomach, belly
--4 has particulars: