An articulation disorder is a problem with making individual speech sounds. Sounds can be substituted, omitted, changed or added. An articulation disorder typically affects one or a few sounds individually. For example, a child may substitute a 'w' sound for a 'l' sound as in 'wake' for 'lake,' or an 'f' for a 'th' sound as in 'fink' for 'think.'
A phonological disorder involves patterns of sound errors that affect classes of sounds and continues longer than what is considered developmentally appropriate. Children will use phonological processes such as syllable reduction (e.g. saying ‘nana’ for banana’) or fronting (substituting sounds made in the back of the mouth for sounds made in the front of the mouth as in ‘tar’ for ‘car’ or ‘doe’ for ‘go’). Children use phonological processes to simplify speech patterns when they are first learning to talk, but when they continue to use them beyond what is considered normal for their age, a phonological disorder may be present.