The best replacement for permutation is combination.

The best alternatives to permutation are rated as following:
★★★★★  combination
★★★  computation
★★  combination probability
★  combination definition
★  combinations
★  combination math
★  combination gmat
  combination formula
  anagram
  arrangement

Your alternative for permutation is not listed? Suggest!
Speaking about permutation, one probably shouldn't forget about replacement.

Other search terms related to permutation and their ratings are:
★★★★★ replacement
★★★★ repetition
You have in mind a companion for permutation and it is not yet here? Propose!



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permutation
combination
computation