Two-valued. A binary relation states how two kinds of elements are linked, e.g., "is married to", "is talking with", "is larger than", "precedes" . A binary alphabet contains two kinds of characters, e.g., "0" and "1", "yes" and "no." A distinction, e.g. between "inside" and "outside", is a binary operation. Binary contrasts with unary = one-valued, ternary = three-valued, etc. (krippendorff )
