Diachrony
I survey the history of work in historical morphology and recent advances in the study of morphological change. Morphology has played an important role in historical linguistics, from arguments concerning constraints on the regularity of sound change, to language classification. I describe how inflectional morphology interacts with other linguistic systems in language change (particularly phonology and syntax), and discuss arguments regard the autonomy of morphology change. Morphology has been considered quite stable in language, which would appear to make it a valuable source of evidence for the reconstruction of remote genetic relationships; however, while several families have been proposed where the argument relies on morphological categories alone, such evidence does not constitute a reliable argument for relationship in the absence of cognate material.