Almost Disjoint Sets - Other Meanings

Other Meanings

Sometimes "almost disjoint" is used in some other sense, or in the sense of measure theory or topological category. Here are some alternative definitions of "almost disjoint" that are sometimes used (similar definitions apply to infinite collections):

• Let κ be any cardinal number. Then two sets A and B are almost disjoint if the cardinality of their intersection is less than κ, i.e. if

The case of κ = 1 is simply the definition of disjoint sets; the case of

is simply the definition of almost disjoint given above, where the intersection of A and B is finite.

• Let m be a complete measure on a measure space X. Then two subsets A and B of X are almost disjoint if their intersection is a null-set, i.e. if

• Let X be a topological space. Then two subsets A and B of X are almost disjoint if their intersection is meagre in X.