• → DisjointQ

ArrayQ

WMA

ArrayQ[expr]

tests whether expr is a full array.

ArrayQ[expr, pattern]

also tests whether the array depth of expr matches pattern.

ArrayQ[expr, pattern, test]

furthermore tests whether test yields True for all elements of expr.
ArrayQ[expr] is equivalent to ArrayQ[expr, _, True&].

• • ArrayQ[a]

• • ArrayQ[{a}]

• • ArrayQ[{{{a}},{{b,c}}}]

• • ArrayQ[{{a, b}, {c, d}}, 2, SymbolQ]