Bilingualism is commonly defined as the use of at least two languages by an individual (ASHA, 2004). It is a fluctuating system in children and adults whereby use of and proficiency in two languages may change depending on the opportunities to use the languages and exposure to other users of the languages. It is a dynamic and fluid process across a number of domains, including experience, tasks, topics, and time. 

  • Simultaneous bilingualism occurs when a young child has had significant and meaningful exposure to two languages from birth. Ideally, the child will have equal, quality experiences with both languages.
  • Sequential bilingualism occurs when an individual has had significant and meaningful exposure to a second language, usually after the age of 3 and after the first language is well established. These second language learners are referred to as "English language learners" in U.S. schools.

The "bilingual" experience is unique to every individual. There is variability in the amount and quality of exposure to the languages the individual learns, as well as the experiences he or she has using the languages when interacting with others.


American Speech-Language-Hearing Association. (2004). Knowledge and Skills Needed by Speech-Language Pathologists and Audiologists to Provide Culturally and Linguistically Appropriate Services [Knowledge and Skills]. Available from

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