The term 'deteriorate slowly' can be described by the five-letter word 'ERODE'. Eroding is a gradual process of wearing away or weakening something, such as land or structures, through the action of wind, water, or other natural elements. This process is often seen in nature, where rivers and streams ERODE the banks of their beds, or where wind and rain ERODE the surface of rocks. In addition, erosion can also occur due to human activities, such as deforestation or overgrazing. Ultimately, the process of erosion leads to the deterioration of whatever is being eroded.