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Giang T. Pham, Ph.D., CCC-SLP
San Diego State University

Vietnamese is an Asian tonal language spoken by 100 million people in Vietnam and worldwide (click here for information on Vietnamese Americans). We have just begun to study developmental language disorder (DLD) in the Vietnamese language. An important first step was to identify children with DLD in Vietnam, where speech-language pathology is a new field, and DLD is not yet a recognized disability. To identify children with DLD, we measured children’s language skills using several different tasks, compared them to peers, and consulted parents and teachers who knew the children best. This post summarizes what we currently know about the general characteristics of Vietnamese children with DLD and potential signs of the disorder.

Vietnamese children with DLD, like all children with DLD, have difficulty learning language even though they do not have sensory or intellectual disabilities. Table 1 shows some of the language differences we found between 5-year-old children with typical development and children with DLD in Vietnam. Children with DLD had limited vocabulary, shorter sentences, simpler sentence structures, and more grammatical errors. They also have more difficulty repeating word and sentence-level information.

Table 1. General language characteristics of Vietnamese children with DLD
Typical DLD
Expressive vocabulary 83% correct 59% correct
Sentence length 7.5 syllables/utterance 4.8 syllables/utterance
Sentence complexity 1.2 clauses/utterance 0.7 clauses/utterance
Grammaticality 88% grammatical utterances 49% grammatical utterances
Sentence repetition 82% sentences correct 56% sentences correct
Nonword repetition 61% syllables correct 43% syllables correct
Summarized from Pham and colleagues, 2019, and Pham and Ebert, 2020

While there are general characteristics of DLD across languages, children with DLD also make errors that are specific to the language or languages they are learning. Children with DLD often make the same kinds of errors as their typical peers, though the number of errors may be greater and may continue for a longer time. Studying typical language development can help us identify errors commonly found in Vietnamese that might be more common in children with DLD.

From the handful of studies on typical Vietnamese grammatical development, we know that one common error pattern is classifier omission. Classifiers are a type of word that goes before a noun and provides some information about the noun itself. For example, the Vietnamese classifier con indicates that something is alive. It is required in certain phrases such as counting: Saying “three bears” in Vietnamese is ba con gấu [three classifier bear], not ba gấu [three bear]. Monolingual Vietnamese toddlers and preschoolers show classifier omissions as they are developing their language skills. Bilingual children who speak Vietnamese as a first language make this error into the early school years.

Our initial results show that classifier omission is a common error for monolingual Vietnamese-speaking kindergarteners with DLD. Here is an example:

  • Child: Cậu bé làm rơi bóng.
  • Adult target: Cậu bé làm rơi quả bóng.
  • English Gloss: [Boy drop (missing classifier) balloon]

We will follow these kindergarteners over time to see whether this error persists longer for children with DLD.

In sum, we are making progress in understanding signs of DLD in Vietnamese speakers. There are now more tools to measure Vietnamese speech and language skills (see list here). Included in this list are the assessment tools created from our research that are now publicly available:, which can be used by examiners fluent in Vietnamese or in collaboration with an interpreter. Still, more work is required to address the clinical needs of Vietnamese children with DLD around the world as well as the research gaps in Vietnamese language development, accurate identification, and effective treatment. Our research team will continue the search for effective indicators of DLD in Vietnamese, whether a child is learning Vietnamese as a single language or in a bilingual environment.

  1. Dam, Q.D., Pham, G., Potapova, I., & Pruitt-Lord, S. (2020). Grammatical characteristics of Vietnamese and English in developing bilingual children. American Journal of Speech-Language Pathology, 29, 1212-1225.
  2. Pham, G. & Ebert, K. (2020). Diagnostic accuracy of sentence repetition and nonword repetition for Developmental Language Disorder in Vietnamese. Journal of Speech, Language, and Hearing Research, 63, 1521–1536.
  3. Pham, G., Pruitt-Lord, S., Snow, C.E., Nguyen, H.T.Y., Phạm, B., Dao, T.B.T., Tran, N.B.T., Pham, L.T., Hoang, H.T., & Dam, Q.D. (2019). Identifying developmental language disorder in Vietnamese children. Journal of Speech, Language, and Hearing Research, 62, 1452-1467.
  4. Tran, J. (2010). Child acquisition of Vietnamese classifier phrases. Journal of Southeast Asian Linguistics Society, 3, 111-137.