numel gives you total number of elements present in the array. i.e. it is product of result of size function.
A = rand(10,3) ;
numel(A)
size(A,1)*size(A,2)
length gives you maximum number of size or which ever is dominant along row and column.
A = rand(10,3) ;
length(A)
size(A,1)
%
B = A' ;
length(B)
size(B,2)
