metathesis

/mə.ˈtæ.θə.sɪs/
noun
  1. 1

    The transposition of letters, syllables or sounds within a word, such as in ask as /æks/.

  2. 2

    The double decomposition of inorganic salts.

  3. 3

    The breaking and reforming of double bonds in olefins in which substituent groups are swapped.

Source: https://en.wiktionary.org/wiki/metathesis