What is the definition or description of: language impairment?

Language impairment: "A Language impairment is defined as a disorder in one or more of the basic learning processes involved in understanding or in using spoken or written language. " See: http://www.fldoe.org/academics/exceptional-student-edu/ese-eligibility/language-impairment-li.stml. This can include: Phonology , Morphology, Syntax, Semantics & Pragmatics.