Describe a phonological disorder.

A phonological disorder is characterized by difficulties in understanding or applying the rules that govern sound patterns in speech. This means that an individual may struggle with recognizing how sounds function and pattern in their language, which can lead to consistent errors in speech production. For instance, a child might substitute certain sounds for others, delete sounds, or simplify complex sound patterns. These issues are not just related to the articulation of specific sounds but rather involve a deeper cognitive understanding of the systematic nature of sound use in language.

The other choices describe different concepts. A developmental condition causing stuttering relates to fluency issues rather than phonological processing. A rare speech sound typically absent in language points to a specific phonetic sound, which does not encompass the broader patterns of sound creation and usage that define phonological disorders. Lastly, a condition affecting only the clarity of speech suggests an articulation disorder, which is more about accurately producing sounds rather than understanding and utilizing the sound rules within a language context. Thus, the correct answer emphasizes the cognitive aspects of sound pattern rules that are central to phonological disorders.