 But there are some cases in which the sum can be known to behave nicely. If all the terms in the sequence are positive, and there is some order in which their sum converges, then their sum must converge to this value in any order. This is because the partial sums form an increasing sequence, and for any two orderings of the terms, and any partial sum of one of those orderings, there must be some partial sum of the other ordering that includes all of the terms in that partial sum, and vice versa. Similarly, the value of the sum doesn’t depend on the order of summation if all the terms are negative. And if the positive terms have a convergent sum, and the negative terms of a series also do, then the sum of the series taken in any order must be equal to the sum of these two sums. Such a sequence is said to be absolutely convergent, as the sum of the absolute values of the terms converges.