Most children make some mistakes as they learn to say new words. A speech sound disorder occurs when mistakes continue past a certain age. Every sound has a different range of ages when the child should make the sound correctly. Speech sound disorders include problems with articulation (making sounds) and phonological processes (sound patterns).

The information above is a summary of articles as found at the following:

American Speech Language Hearing Association Website (n.d.).  Typical Speech and Language Development.