Deep Dives

The Issue

Educators and clinicians often encounter multiple and seemingly overlapping diagnoses and labels in students’ IEPs and educational records. One term that has gained increasing visibility recently is developmental language disorder (DLD), making many question the use of this term in place of others that they may be more familiar with, such as specific language impairment, mixed receptive/expressive language disorder, or a host of others. Questions often arise about how exactly a diagnosis of DLD differs from dyslexia- especially given all of the mentions of language in the International Dyslexia Association’s (IDA’s) revised 2025 definition (IDA, 2025)- or how this label aligns and diverges with other literacy disorders such as specific learning disorder (SLD) with impairment in reading comprehension. This article seeks to clarify these distinctions and explain why the term DLD warrants broader understanding in educational contexts.

Diagnosis vs. Eligibility

The first step in understanding why there are so many labels that seem to reference the same or similar cluster of symptoms (and why a student may have more than one similar-sounding label found within their records) is that diagnosticians are pulling from one of three different classification systems.

• The Diagnostic and Statistical Manual of Mental Disorders, 5th edition Text Revision (DSM-5 TR) is published by the American Psychiatric Association (APA) for U.S.-based clinicians, and provides detailed diagnostic criteria for a range of mental, behavioral, and neurodevelopmental disorders. Children with persistent difficulties acquiring language across modalities fall under the diagnosis of language disorder in the DSM-5 TR. This label replaced the term mixed receptive-expressive language disorder in the previous edition of the DSM, and might still be found in older documentation and reports. The DSM-5 TR has a distinct label for social (pragmatic) communication disorder as well, which someone may have in addition to, or instead of, language disorder, depending on the domains of language impacted.
• The International Classification of Diseases, 11th edition (ICD-11) is published by the World Health Organization (WHO) for international use across all health conditions, providing shorter, general descriptions of diagnoses that are primarily used for insurance billing. A child diagnosed with language disorder under the DSM-5 TR would likely meet criteria for developmental language disorder under the ICD-11, as the constructs are closely aligned but defined within different systems (First et al., 2021).
• EdCode eligibility categories are based on the Individuals with Disabilities Education Act’s (IDEA’s) broad description of speech or language impairment (SLI), and requirements to fit this category can vary by state.

Labels such as DLD are not prohibited under IDEA and can be referenced in evaluation and IEP documentation (Office of Special Education Programs [OSEP], 2023). However, eligibility decisions in public schools are made under state-defined IDEA disability categories, and services are based on individual student needs rather than diagnostic labels. As a result, they are less likely to use terms such as DLD (or dyslexia) even if students would otherwise meet diagnostic criteria for these labels had they received a private assessment outside of the school. It’s important to understand that the terms diagnosis and eligibility category are not synonymous. Some students meet diagnostic criteria for DLD (or dyslexia, autism, etc) but are not eligible for special education services through their public school district. In these cases, the IEP report and recommendations are in no way invalidating previous reports or diagnoses- they are working with a different set of parameters.

Understanding DLD

DLD is part of a larger category of spoken language disorders, which involve continued challenges with understanding and expressing language (ASHA, n.d.). The term “developmental” is used to describe that the condition has been present throughout the child’s development of language, even if it wasn’t diagnosed through early intervention. That is, it means that the child’s language difficulties have always been present to some extent, rather than acquired through a traumatic medical event such as a brain injury from a severe accident or stroke. This term is also the diagnosis used when a person’s language difficulties are not secondary to a primary condition such as Down syndrome or autism (ASHA, n.d.).

Language difficulties associated with DLD may affect one or more of the primary domains of spoken language, including phonology, morphology, semantics, syntax, and/or pragmatics. The examples below illustrate how DLD might present; however individual profiles may vary considerably, and this list is not exhaustive:

• Phonology
  • Difficulty perceiving, remembering, or manipulating speech sounds
  • Weak phonological awareness (e.g., segmenting, blending, manipulating sounds)
• Semantics
  • Using overly simplistic and/or vague words
  • Word finding difficulty
  • Limited depth of vocabulary knowledge
  • Difficulty learning new words efficiently
• Syntax
  • Using short, simple sentence structures and phrases
  • Difficulty using and/or understanding lengthy or complex sentences (e.g., embedded clauses, passives, conditionals)
• Morphology
  • Omission or erroneous use of verb tenses or other word endings
  • Difficulty interpreting or using derivational morphology (e.g., happy → happiness)
• Pragmatics
  • Unorganized narratives and explanations
  • Inappropriate amount of details shared (either too many tangential and unnecessary details or insufficient details for the listener to understand)

Yet in the classroom, these deficits are often masked in oral language due to the simplicity of everyday speech. DLD has been described as a “hidden” disorder because its features are less immediately visible than many other neurodevelopmental conditions, and affected students may not be identified despite facing significant educational impact (McGregor, 2020). Many of the above characteristics demonstrated by children with DLD, such as using vague or overly simplistic vocabulary and telling disjointed stories, are common for many children, and using single-word responses or short phrases rather than complete sentences while conversing is also often expected.

Also consider that the oral language that children are exposed to tends to be relatively simple, often with routine, repetitive vocabulary and simple syntax. Written language, even texts written for children, tends to contain more sophisticated vocabulary and complex sentence structures than spoken language, even conversations between adults (Montag, 2019). Children with DLD are also often able to compensate for receptive language difficulties by picking up on context clues, reading nonverbal communication, and mimicking the behaviors of their classmates.

Compounding these challenges, classroom teachers are not trained to identify language disorders. Studies have also shown that teachers report feeling ill-prepared to identify spoken language deficits (Dockrell & Lindsay, 2001; Sadler, 2005), and empirical evidence supports these concerns. When teachers’ ratings of first-grade students’ language abilities were compared to standardized screening results, ratings showed low sensitivity and specificity- meaning teachers often failed to identify students who had language difficulties and sometimes even identified difficulties where none were present (Antoniazzi et al., 2010).

For these reasons (and several others outside the scope of this article), DLD is significantly underdiagnosed (Prelock et al., 2008), and has been for decades (Tomblin et al., 1997). Yet DLD affects over 7% of children (Norbury et al., 2016), making it one of the most common neurodevelopmental disorders, many of whom are not identified or served (McGregor, 2020). When students’ language difficulties are noticed, it is often not because of the child’s difficulty with oral language, but because of their difficulty with reading comprehension (Adlof & Hogan, 2018). In some cases, students whose primary observable difficulty is reading comprehension may instead receive a specific learning disorder or disability label related to reading comprehension. While this label captures the academic manifestation of the difficulty, it does not necessarily reflect the broader oral language weaknesses that may be present.

DLD and Literacy

Reading comprehension is often described, through the Simple View of Reading, as the product of word recognition and language comprehension (Gough & Tunmer, 1986; Hoover & Gough, 1990). More recent models have expanded this framework, highlighting additional contributors such as executive functioning, cognitive flexibility, background knowledge, and motivation (Duke & Cartwright, 2021; Kim, 2017). In this sense, the Simple View may be incomplete, but it is not incorrect. Language comprehension remains a necessary component of reading comprehension, even if it is not the only one. Therefore, when students experience reading comprehension difficulties, oral language skills must be examined as part of the profile, even though they may not be the sole source of difficulty (Cain & Oakhill, 2007; Catts et al., 2006; Guo et al., 2013; Nation & Norbury, 2005; Spencer & Wagner, 2018; Spencer et al., 2020).

While DLD is a disorder primarily of spoken language, it unsurprisingly affects students’ ability to understand written language as well. The aforementioned sophistication and complexity of written language often challenge those with language disorders. Students with DLD may struggle to comprehend text because written language places sustained demands on vocabulary knowledge, syntactic processing, and discourse-level integration (Montag, 2019; Scott, 2009). Weaknesses in vocabulary depth can limit understanding of nuanced word meanings, while difficulty parsing complex sentences may interfere with interpreting sentences that include multiple ideas, or components such as embedded clauses or passive voice.

But educators may overlook the impact of language skills on reading and spelling individual words as well, especially in less transparent orthographies such as English. 

Take, for example, reading a word like camel. Even with training on Syllable Types and Division strategies, a reader would not be able to determine if the first syllable of this word is pronounced /kā/ or /kă/ unless they had the word camel in their oral vocabulary. It is also likely that students unable to retrieve the appropriate animal name may attempt to apply equal stress to both syllables, rather than producing the typical trochaic pattern with a reduced vowel (schwa) in the second, unstressed syllable. Other language processes, such as morphological awareness, also come into play when reading- and especially spelling- words. If a child is trying to spell the spoken word /mĭst/, for example, they would have to have either a definition or example sentence provided and subsequently apply their language skills to extract whether the target word is the noun (mist) or regular past tense verb (missed), and then apply morphological knowledge to appropriately spell the last sound as <ed> rather than <t> if appropriate.

Although earlier theoretical models of reading tended to separate word recognition from language comprehension, more recent frameworks recognize that these processes are not fully independent. For example, the Active View of Reading highlights vocabulary and morphological awareness as part of a bridging process that contributes to both decoding and comprehension (Duke & Cartwright, 2021), illustrating why oral language weaknesses may influence not only their understanding of a text, but also the accuracy of word reading itself. This interconnectedness between oral language and word-level reading is one reason that DLD and dyslexia are sometimes conflated, particularly since literacy difficulties can be a more visible concern. Without careful attention, educators may overlook students’ underlying language needs, misinterpret reading struggles, or select instructional approaches that do not address the source of the breakdown (Glasby et al., 2022).

Dyslexia and DLD

You may have heard about the updated definition of dyslexia put out by the International Dyslexia Association (IDA) in October 2025:

“Dyslexia is a specific learning disability characterized by difficulties in word reading and/or spelling that involve accuracy, speed, or both and vary depending on the orthography. These difficulties occur along a continuum of severity and persist even with instruction that is effective for the individual’s peers. The causes of dyslexia are complex and involve combinations of genetic, neurobiological, and environmental influences that interact throughout development. Underlying difficulties with phonological and morphological processing are common but not universal, and early oral language weaknesses often foreshadow literacy challenges. Secondary consequences include reading comprehension problems and reduced reading and writing experience that can impede growth in language, knowledge, written expression, and overall academic achievement. Psychological well-being and employment opportunities also may be affected. Although identification and targeted instruction are important at any age, language and literacy support before and during the early years of education is particularly effective” (International Dyslexia Association [IDA], 2025).

This revised definition of dyslexia helps educators and practitioners better understand the scope, causes, and developmental presentation of the disorder. However, it does not alter how students are diagnosed or determined eligible for services in schools. Diagnostic criteria remain governed by the DSM-5 TR, and eligibility decisions are based on state-defined IDEA categories. Because the IDA operates independently of these classification systems, its updated definition does not automatically change policy or practice, though it may influence future revisions.

Among other changes, the updated definition emphasizes the role that language skills play in dyslexia. Many students with dyslexia exhibit relatively weak oral language skills- particularly in areas such as vocabulary breadth, morphology, and syntactic comprehension, even if they don’t meet the threshold for a diagnosis of DLD (Adlof et al., 2017; Bishop et al., 2009; McArthur et al., 2000; Ramus et al., 2013). Dyslexia and DLD do also frequently co-occur. Estimates vary, but studies suggest that roughly one third of children with DLD also meet criteria for dyslexia (Catts et al., 2005), while approximately 15–20% of children with dyslexia meet criteria for DLD (Catts et al., 1999, 2005). These figures may underestimate the true rate of co-occurrence due to differences in sampling and diagnostic criteria (McArthur et al., 2000).

As Adlof and Hogan (2018) note, it may be helpful to conceptualize three possible profiles: dyslexia without DLD, DLD without dyslexia, and co-occurring dyslexia and DLD. These profiles differ not only in the breadth of language weaknesses, but also in expected literacy outcomes. Children with dyslexia alone may show relatively subtle oral language weaknesses, whereas children with DLD often demonstrate broader oral language deficits that affect comprehension. Those with co-occurring dyslexia and DLD tend to exhibit the most pervasive and severe reading comprehension challenges, reflecting the combined impact of word-level and broader language weaknesses.

While students with DLD may also experience word-reading difficulties- and students with dyslexia may show oral language weaknesses- the presence of shared linguistic foundations does not mean the disorders are interchangeable or that they require identical instructional responses. Some research has also begun to explore how the presentation of phonological deficits might differ when exhibited by those with dyslexia as opposed to those with DLD. For example, Ramus et al. (2013) found evidence for at least two partially distinct components within the domain of phonology: phonological skills (e.g., phonological awareness and phonological working memory) and phonological representations (e.g., phonological discrimination and categorization). The study showed that children with SLI (which often overlaps with DLD) and children with dyslexia show partly distinct profiles across these dimensions, potentially because of how these components contribute to either written or oral language. Importantly, because phonological processing interacts closely with broader language systems, weaknesses in either component may have downstream effects beyond word reading, influencing vocabulary growth, spelling, and aspects of morphological and syntactic development (Adlof et al., 2006; Carlisle, 2003; Farquharson et al., 2017; Rvachew & Grawburg, 2007).

In Sum

Both DLD (or similarly-named language impairment) and dyslexia can be exhibited by phonological, morphological, and/or other language challenges, as well as word-reading and/or reading comprehension challenges. In fact, these disorders may be indistinguishable to a classroom teacher. But while there is a high prevalence of comorbidity of DLD and dyslexia, these are distinct disorders that differ in the breadth and primary focus of the language difficulties involved.

Regardless of what diagnoses students do or don’t have in their academic file, educators need to target the skills that the student struggles with. That is to say, a child may struggle with phonology due to an underlying phonological processing disorder, having dyslexia, being an English Learner, or simply having a relative weakness in this area despite not rising to any diagnostic threshold. Regardless, the student would benefit from direct instruction and practice in this area. 

Dyslexia and developmental language disorder are best understood not as competing labels, but as potentially partially overlapping profiles within a broader language system. Both can involve weaknesses in phonology, morphology, and other linguistic processes; both can affect reading; and both may co-occur in the same student. The distinction lies less in whether language is involved and more in the breadth, severity, and developmental course of those language difficulties. For educators, the goal is not to sort students into rigid categories, but to recognize how underlying language systems are either supporting or constraining literacy development. Because its features are often subtle in everyday conversation, students with DLD may be misidentified as simply poor readers or overlooked entirely, delaying access to language-based interventions that directly target their individualized needs in vocabulary, syntax, morphology, and/or discourse. Clearer terminology can sharpen that understanding, but effective instruction ultimately depends on identifying and addressing the specific linguistic demands that are breaking down for a given learner.