Aphasia is an acquired language disorder due to brain damage that affects the production and comprehension of spoken and written language in varying degrees and patterns depending on the size and site of the lesion. Errors in speech production have been reported among aphasics. Errors in production can be either phonemic, involving language-based deformations, or phonetic, involving a motor planning deficit. The deficits can be said to be at the phonological level when the incorrect phonological form of the word is selected but is implemented correctly, and at the phonetic level when the correct sound segments are selected but articulatory implementation is impaired. Phonetic deficits are not linguistic. Most aphasics produce phonological errors in their speech in the form of substitution, omission, addition, or distortion(neologism), which are called "phonemic" (or "literal") paraphasias. Aphasia research on the nature of phonological breakdown as to whether the deficit is phonetic or phonemic in the different aphasia syndromes reveals contradictory results.