ambilingualism en · NOUN
Etymology
From ambilingual + -ism.
Meanings
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(uncountable) The condition of being ambilingual; the ability to speak two or more languages with nativelike proficiency and fluency, treating them as completely equal without dominance of one over the other.
As has been noted, bilingualism is frequently still assumed to be synonymous with ambilingualism (i.e. native-like competence in both languages), although researchers in bilingualism have identified a large number of forms depending on whether the respective definition concentrates on age of acquisition, order and sequence of acquisition, mental organisation, function, level of proficiency or/and social aspects involved.
2002, Philip Herdina, Ulrike Jessner, A Dynamic Model of Multilingualism: