as ‧ so ‧ nance /ˈæsənəns/ BrE AmE noun [uncountable] technical
[ Date: 1700-1800 ; Language: French ; Origin: Latin assonare 'to answer with the same sound' , from ad- 'to' + sonare 'to sound' ]
similarity in the vowel sounds of words that are close together in a poem, for example between ‘born’ and ‘warm’