The literal definition of missing someone is to perceive with regret the absence or loss of that person in your life. The emotional impact of missing someone is much more complex.
When a person misses another person in their life, it is typically attributed to the fact that they love them. Emotionally, missing someone is one of the many expressions of love.
The psychological factors behind missing someone are also important. A person who is lonely and sees a world where other people are sharing and loving each other can find themselves missing someone because they are not feeling any love in their life.
Many believe that missing someone is associated with the knowledge that person brought into that person's life. A student misses a teacher because that teacher opened new worlds to that student by introducing the student to his or her insights.
Typically, someone misses a person because they perceive a sense of value in the relationship with that person. The value is associated with romantic love, friendship, intellectual stimulation or happiness. A man misses the woman he fell in love with after she leaves. A woman misses the daily talks she shared with a co-worker who listened to her problems. A professor misses the colleague with whom he shared daily debates. These are the many reasons why people miss another person.