Question

abc + bca + cab is a ___.

Answer 1

As a $\times$ b $\times$ c = b $\times$ c $\times$ a = c $\times$ a $\times$ b = abc = bca = cab
All the three terms are same.
So they are like terms and can be added to get a single term.
abc + bca + cab = 3abc or 3bca or 3cba
So it is a monomial.