To declare somebody persona non grata is to state that they are ostracised or unwelcome. It usually means somebody, usually a diplomat, is forbidden by the government from entering or staying in a certain country. It can also be used in a non-diplomatic context to refer to somebody who has been shunned by a group of people for whatever reason they see fit.
‘Persona non grata’ is a Latin term, literally translating to ‘person not acceptable,’ is a Latin term which is neither part of the classical nor New Latin language. It has, however, been in use since as early as the 15th century.
When pluralised, persona non grata is sometimes erroneously written as personas non grata. This is incorrect; the plural version of the term should be written as personae non grata, as within Latin.
Persona non grata is used in mostly a formal, legal context, but informal use is not unheard of. Examples of use in a sentence include:
“The spies were deported as persona non grata.”
“Bob found himself persona non grata at the party after the incident the previous weekend.”