This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.
If a word conforms to a special rule, I call it an Isolated Word™.
Use the following examples to find the rule:
Isolated Words™,Not Isolated Words™ Reclusive,Affable Abandoned,Cordial Empty,Convivial Aloof,Upbeat Singular,Receptive