metathesis

Concise Oxford English Dictionary © 2008 Oxford University Press:
metathesis /mɪˈtaθɪsɪs/

▶noun (pl. metatheses /-siːz/)

• 1 Grammar the transposition of sounds or letters in a word.

• 2 Chemistry another term for double decomposition.

– derivatives
metathetic /ˌmɛtəˈθɛtɪk/ adjective,
metathetical adjective.

– origin C16: from Gk, ‘transposition’.