So far, I have two of the examples . . .
What are naturally occuring examples of relations that satisfy two of the
following properties, but not the third: Reflexive, Symmetric, and Transitive?
Let = "is a brother of"
. . (The first is male, and both parties are children of the same parents.)
Not necessarily true . . .
The relationship is reflective and transitive, but not symmetric.
Let = "knows" (is acquainted with).
. . .True.
. . .True
. . .not necessarily true
The relationship is reflexive and symmetric, but not transitive.