P.M. is short for post meridiem, which is Latin for "afternoon." It is commonly used to indicate the time of day from 12:00 p.m. (noon) to 11:59 p.m. (midnight). However, there are many synonyms that can be used to describe this same time period. Some examples include afternoon, evening, nighttime, dusk, and twilight. For formal settings, it is best to stick with using "p.m." or "post meridiem." However, in casual conversation, these synonyms can be used to add variety and clarity to our communication. Regardless of which synonym you choose, it's important to be clear and specific when referring to the time of day.