Phonological disorders are a functional speech sound disorder related to the motor production of speech sounds and to the linguistic aspects of speech production. Phonological disorders focus on predictable, rule-based errors (e.g., fronting, stopping, and final consonant deletion) that affect more than one sound. It is often difficult to clearly differentiate between articulation and phonological disorders; therefore, many researchers and clinicians prefer to use the broader term, "speech sound disorder," when referring to speech errors of unknown cause.