1.NounA subbranch of combinatorics that concerns additive problems expressed using sumsets."One major area of study in additive combinatorics is that of inverse problems: for instance, given the sumset
A
+
B
{\displaystyle A+B}
is small in size, what can we say about the structures of
A
{\displaystyle A}
and
B
{\displaystyle B}
? In the case of integer sumsets, Freiman's theorem provides a partial answer."