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the name used in Russian chronicles to refer to the Balto-Finnish Suomi tribe, which settled on the southwest coast of Finland early in the first millennium A.D. After subjugating the Sum’ in the mid-12th century, the Swedish feudal lords began the conquest of Finland. Subsequently, the Sum’, Häme, and western Karelian tribes combined to form the Finnish nationality.
the result of the addition of such quantities as numbers, functions, vectors, or matrices. In all cases the commutative and associative laws hold; moreover, if multiplication is defined for the quantities in question, then it is distributive over addition. Thus, the following relations are satisfied:
a + b = b + a
a + (b + c) = (a + b) + c
(a + b)c = ac + bc
c(a + b) = ca + cb
In set theory, the sum, or union, of sets is the set whose elements belong to at least one of the given sets.
inA : A -> A+B inB : B -> A+B inA(a) = (0,a) inB(b) = (1,b)
and a disassembly operation:
case d of isA
This can be generalised to arbitrary numbers of domains.
See also smash sum, disjoint union.
Unix manual page: sum(1).