What is speech?

The terms ‘speech’ and ‘language’ are NOT the same although they are often used interchangeably. Speech is purely about a person’s ability to say words. It involves using the lips, tongue, teeth, voice and respiration support to articulate sounds and then to sequence these sounds into words.


What is articulation?

Articulation refers to the production of speech sounds. Articulation involves planning and executing the smooth sequence of sounds that result in speech.


What are phonological processes?

Phonology is related to the sound system and to rules for the combination of sounds, to form words and create different meanings. Take for example the words load and low. While the child may be able to produce the /d/ sound, they may not be able to use it in the word-final position. If the child produces the word load without the /d/ sound, they create a difference in the word meaning. This is an example of a phonological process.



Intelligibility refers to a judgement made by a clinician based on how much of what a child says can be understood by an unfamiliar person. Factors which influence intelligibility include the number, type and consistency of speech sound errors. According to Weiss (1982) by 18 months a child's speech is normally 25% intelligible, by 24 months their speech is normally 50-75% intelligible and by 36 months a child's speech is normally 75-100% intelligible.


What is a speech disorder?

Speech disorders is a broad term, which encompasses articulation disorders, phonological disorders, and suspected childhood apraxia of speech. An articulation disorder refers to the inability to produce particular speech sounds, or to difficulties with the motoric production of speech. According to several studies articulation disorders represent a deficiency in relative peripheral motor processes that lead to speech.


Omissions¹, substitutions², additions³ and distortionsā“ of speech sounds decrease the overall intelligibility of speech and are common articulatory errors. Impairments of the representation and organisation of sounds within a language system, is known as a phonological disorder. Current thinking suggests that a phonological disorder reflects a central deficiency, explicitly, a neurolinguistic dysfunction at the phonological level, though research is still required in this area.

1. Omission refers to a sound that has been left out, e.g. ‘top’ - ‘stop’

2. Subsitituions refer to a sound that has been swapped for another sound, e.g. ‘wed’ – ‘red’

3. Addition refers to a sound that has been added ‘spwoon’ – ‘spoon’

4. Distortions refers to a sound that is produced with incorrect tongue placement, e.g. ‘thee’-‘see’


-Bauman-Waengler, J. (2004). Articulatory and phonological impairments: A clinical focus. (2nd Edition). Boston: Pearson.

-Bowen, C. (2007). Typical Speech Development.--Retrieved June 3, 2009 from http://www.speech-language-therapy.com/Table3.htm

-Bowen, C. (2007). Phonological Processes.--Retrieved June 3, 2009 from http://speech-language-therapy.com/Table2.htm

-Elbert, M., & Gierut, J. (1986). Handbook of clinical phonology: Approaches to assessment and treatment. San Diego, CA: College-Hill Press.

-Grunwell, P. (1987). Clinical phonology. (2nd Edition). Baltimore: Williams & Wilkins.

-Joffe, B., & Serry, T. (2004). The evidence base for the treatment of articulation and phonological disorders in children. In S. Reilly, J. Douglas, & J. Oates, (Eds). (2003). Evidence-based practice in speech pathology. (pp. 259-287) London: Whurr.

-Silverman, F.H. (1995). Speech, language and hearing disorders. Boston: Allyn & Bacon.

-Skinner, P.H., & Shelton, R.L. (1985). Speech, language and hearing: Normal processes and disorders. (2nd Edition). New York: John Wiley.

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