What is loneliness?

As some readers may know, loneliness is a topic I'm very interested in and continue to speak and write about. For the next few entries I want to go through some basics with it.
​
What is loneliness? 
It’s interesting how in looking at the definition of loneliness at Merriam-Webster online, it gives definitions that don’t jive with mine. M-W.com defines “lonely” as:
1. a: being without company
b: cut off from others
2. not frequented by human beings
3. sad from being alone
4. producing a feeling of bleakness or desolation
 
While I don’t discount any of those definitions, the more I study loneliness, the more I begin to side with the meaning given by John Cacioppo, the late social neuroscientist. He wrote, “Loneliness is defined as a distressing feeling that accompanies the perception that one’s social needs are not being met by the quantity or especially the quality of one’s social relationships.” In other words, loneliness is what you feel when you want connections of a certain type (however that is defined by you) and you don’t have them.