Apraxia of Speech (AOS)—also referred to as acquired apraxia of speech, verbal apraxia, or childhood apraxia of speech (CAS) in the case of pediatric diagnosis—is a neurological speech disorder. Apraxia of Speech (AOS) can also manifest as a symptom of neurodegenerative conditions, particularly in the non-fluent variant of Primary Progressive Aphasia (nfvPPA). In this context, individuals with nfvPPA may display characteristics of AOS, reflecting the underlying neurodegenerative changes that impact the brain's ability to produce fluent, articulated speech.

Individuals with AOS encounter difficulties in articulating what they intend to express accurately and consistently, due to a disruption in the neural pathways responsible for planning motor actions and sequencing the intricate movements involved in speech, such as those required by the tongue, lips, and jaw. Although the individual's cognitive understanding and intent of speech can be intact, the brain struggles to correctly orchestrate the corresponding physical movements.

However, it's important to distinguish AOS from dysarthria. The latter is a distinct speech disorder resulting from non-cognitive factors, such as muscular weakness or paralysis affecting speech, rather than the planning of movement. While these conditions can coexist in some individuals, complicating the diagnostic process, they are fundamentally different in origin and manifestation.

The impact of AOS varies significantly among individuals. In milder cases, it may only affect the pronunciation of a handful of phonemes or multi-syllabic words. In contrast, severe manifestations can result in incomprehensible speech, severely inhibiting effective verbal communication. In those case, AOS necessitates the employment of alternative communication strategies or aids.