Medical Definition of narcissistic personality disorder. : a personality disorder characterized especially by an exaggerated sense of self-importance, persistent need for admiration, lack of empathy for others, excessive pride in achievements, and snobbish, disdainful, or patronizing attitudes.
For the purposes of sym metry, letâs now move on to the most common variant of syn- , or sym- , which also means âtogether.â A sym phony is the sounding âtogetherâ of many instruments.
1 A synapse is the point of connection between the endfoot of one neuron and the membrane of another. The word is derived from Greek and means to fasten together.. It is at synapses that one cell influences the activity of another.  There are two broad categories of synapses: chemical synapses and electrical synapses.