pattern - What is an Isolated Word™?

_{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

Answer

With the limited examples that we have,

An isolated word is a word which has a similar meaning to, well, isolated

Nothing much to write,

Reclusive, Abandoned, Empty,Aloof,Singular all have almost the same meaning of isolated.. synonyms to a certain extent.

The non-isolated words

Are somewhat antonyms of isolated..