The term slow time scale denotes a phenomenon that occurs over an extended period. However, there are several synonyms available that convey the meaning of slow time scale even more appropriately. For example, the word 'longitudinal' is a common synonym used to describe phenomena that progress steadily and over a prolonged time. The term 'gradual' also describes the gradual or slow progression of an event. Other possible synonyms for slow time scale may include 'protracted', 'extended period', 'lengthy', 'lengthened', 'stretched out' and 'extended'. All of these words can be used interchangeably to describe an event that occurs over an extended or slow time period.