ArrayQ

ArrayQ[expr] gives True if expr is a full array or a SparseArray object, and gives False otherwise.

ArrayQ[expr, patt] requires expr to be a full array with a depth that matches the pattern patt.

ArrayQ[expr, patt, test] requires also that test yield True when applied to each of the array elements in expr.

Examples

Check if an expression is an array:

ArrayQ[{{1, 2}, {3, 4}}]
(* True *)

Check for numeric arrays:

ArrayQ[{{1, 2}, {3, a}}, _, NumericQ]
(* False *)

Please visit the official Wolfram Language Reference for more details.