My textbook has a chapter titled "Permutations with repetitions" in which it discusses certain problems such as scrambling the letters in words which have multiples of some letters. For example:
How many ways are there to rearrange the letters in the word MISSISSIPPI?
What doesn't quite make sense to me is why they use the terminology of permutation:
My intuition tells me these are actually combinations, since it doesn't matter if you have "$S_1 S_2 S_3 S_4$" or "$S_2 S_1 S_3 S_4$" for four adjacent arrangements of the letter "S" in "Mississippi". Indeed, they even use the formulas for combinations in calculating the # of possible arrangements in the above screenshot, so I'm not sure what permutations have to do with it.