Is "isolation" a restricted word?

I am trying to make a table with a class called "isolation". For some
reason, I am getting a parser error:

=> create table cell ( isolation text );
ERROR:  parser: parse error at or near "isolation"

If I just take off the "n", I get:

=> create table cell ( isolatio text );
CREATE

This table had no problems previously; has the word isolation been used
somewhere else as a SQL word? I can't think of why else I am having
problems with the table (the syntax appears to be correct).

Thanks.
-Tony