The best replacement for asymmetry is symmetry.

The best alternatives to asymmetry are rated as following:
★★★★★  symmetry
★★  focal asymmetry
  asymmetry
  tailing factor
  tailing

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

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



Google Trends

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asymmetry
symmetry
focal asymmetry