PM, the abbreviation for post meridian, is used to indicate the time from 12 noon to midnight. But there are several synonyms to this commonly used term like afternoon, dusk, evening, twilight, nightfall, evening time, and nighttime. These words describe the time of day when the sun is no longer visible, and darkness begins to set in. While afternoon is used to describe the time before dusk when the sun is still visible, twilight, evening, and nightfall are used to describe the period when darkness sets in. These synonyms are useful in describing specific periods of time in a day, and they are commonly used in different contexts for effective communication.